bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental and CFD Analysis of a Rack Manifold for High Power Density Liquid-Cooled Rack
Authors: Shahi Pardeep , Heydari Ali , Bansode Pratik , Siddarth Ashwin , Chowdhury Uschas , Miyamura Harold , Modi Himanshu , Agonafer Dereje , Tradat Mohammad , Rodriguez Jeremy 
Published: November 2023

Abstract
Direct Liquid Cooling (DLC) has emerged as a promising technology for thermal management of high-performance computing servers, enabling efficient heat dissipation and reliable operation. Thermal performance is governed by several factors, including the coolant physical properties and flow parameters such as coolant inlet temperature and flow rate. The design and development of the coolant distribution manifold to the Information Technology Equipment (ITE) can significantly impact the overall performance of the computing system. This paper aims to investigate the hydraulic characterization and design validation of a rack-level coolant distribution manifold or rack manifold. To achieve this goal, a custom-built high power-density liquid-cooled ITE rack was assembled, and various cooling loops were plugged into the rack manifold to validate its thermal performance. The rack manifold is responsible for distributing the coolant to each of these cooling loops, which is pumped by a CDU (Coolant Distribution Unit). In this study, pressure drop characteristics of the rack manifold were obtained for flow rates that effectively dissipate the heat loads from the ITE. The pressure drop is a critical parameter in the design of the coolant distribution manifold since it influences the flow rate and ultimately the thermal performance of the system. By measuring the pressure drop at various flow rates, the researchers can accurately determine the optimum flow rate for efficient heat dissipation. Furthermore, 1D flow network and CFD models of the rack-level coolant loop, including the rack manifold, were developed, and validated against experimental test data. The validated models provide a useful tool for the design of facility-level modeling of a liquid-cooled data center. The CFD models enable the researchers to simulate the fluid flow and heat transfer within the cooling system accurately. These models can help to design the coolant distribution manifold at facility level. The results of this study demonstrate the importance of the design and development of the coolant distribution manifold in the thermal performance of a liquid-cooled data center. The study also highlights the usefulness of 1D flow network and CFD models for designing and validating liquid-cooled data center cooling systems. In conclusion, the hydraulic characterization and design validation of a rack-level coolant distribution manifold is critical in achieving efficient thermal management of high-performance computing servers. This study presents a comprehensive approach for hydraulic characterization of the coolant distribution manifold, which can significantly impact the overall thermal performance and reliability of the system. The validated models also provide a useful tool for the design of facility-level modeling of a liquid-cooled data center.
In-Flight Structural Test of a Hoverbike Using Fiber Optic Sensors
Authors: Hwang Yong-Ha , Jang Kwangwoo , Ahn Hyungjoo , Bang Hyochoong , Han Jae-Hung 
Published: November 2023

Abstract
A hoverbike is a vehicle that can fly and hover. Demand for using hoverbikes in various missions, including transport, surveillance, reconnaissance, and infiltration is increasing. While various attempts have been made to develop hoverbikes, there is still a lack of experimental verification on whether the frame structure of a hoverbike can provide sufficient structural strength to withstand extreme loads that may occur during flight without causing damage. Therefore, in this paper, we aim to experimentally investigate the structural characteristics of the hoverbike frame.
KAIST is developing a hoverbike that can load up to 100 kg. As part of the development process, structural tests were conducted on the hoverbike. Fiber Bragg Grating (FBG) sensors were utilized for the structural testing. The FBG sensor is capable of multiplexing, in which several sensors can be placed on one optical fiber and is not affected by electromagnetic interference (EMI).
Structural strength tests were conducted on the carbon pipes that were used for the manufacturing of hoverbike frames. A down-scaled hoverbike was manufactured. When thrust was generated in the prop connected to the main motor, the dynamic characteristics of the frame was measured. FBG sensor was attached to the frame, and frequency analysis was performed by FFT on the frame strain data measured when thrust was applied. A flight test was performed assuming a rapid maneuvering situation. The maximum bending load generated during rapid maneuvering was calculated using frame strain data. The hoverbike frame was modeled with finite elements, and the internal load analysis was performed by assuming the flight load as a static load. Analysis were compared with flight test, and the validity of the finite element model for internal load analysis was confirmed.
High Load NiTi Shape Memory Alloy Actuators: A Study of Cyclic Behavior
Authors: Thüsing Kai , Hofer Andreas , Pagel Kenny , Weck Christian , Drossel Welf-Guntram 
Published: November 2023

Abstract
This paper advances the knowledge of the cyclic thermomechanical behavior and fatigue of high load SMA-Actuators. Due to their small volume and weight, these actuators provide an attractive alternative to conventional actuators. Especially in production plants and machines, where the requirements for installation space and weight are becoming increasingly crucial for a successful manufacturing process, they find a wide field of application. Quite in contrast to small force applications, more massive geometries and new integration concepts of the shape-memory-components (SMC) are substantial. However, well developed semi-finished products are not yet available. Furthermore, this changes mechanical and functional cycle fatigue, an issue well known from wire based small force SMA-Actuators. Comprehending how these changes significantly alter the SMA behavior will eventually enable novel designing and optimizing. Therefore, the cyclic behavior of the SMC is investigated, using a high load SMA-Actuator, that has been designed for integration in machines tools. The SMCs, cycled in the SMA-Actuator have been manufactured with different methods. Here, a classical manufacturing process is compared to an additive process (PBF-LB/M). The additive processed SMCs show microcracks and pores. Nevertheless, the cyclic properties exceed those of the classical processed specimen in all measured properties. Especially the tiny hysteresis, low shortening of the SMC can be highlighted.
Effect of Hysteresis on a Piezoelectric Inverted Beam Energy Harvester
Authors: Zarepoor Masoud , Bilgen Onur 
Published: November 2023

Abstract
Piezoelectric materials have been used in various types of structures to harvest ambient vibration energy by converting mechanical deformation to electrical charge. The harvested power can be used to charge batteries and/or operate low-power electronics such as wireless sensors. So-called linear piezoelectric devices can harvest vibrational energy efficiently only around the resonant frequency of the device. Ambient vibrations are typically multi-tone excitations with broadband frequency content. As a result, nonlinear piezoelectric harvesters are developed to harvest energy across a wide frequency band. For example, bistable piezoelectric material-based vibration energy harvesters are nonlinear devices with two equilibria, capable of producing large-amplitude motion between the two equilibria where mechanical energy that can be converted to electrical power. An inverted beam with a tip mass can be designed to be bistable and harvest vibrational energy at low frequencies. The tip mass can be selected to place the inverted beam near buckling to cause large geometrically nonlinear deformations at low excitation frequencies. The mathematical modeling dynamical behavior of an inverted beam with a tip mass has been previously investigated. This paper explores the effects of piezoelectric material nonlinearity and hysteresis on the harvested power of an inverted beam vibration energy harvester. This paper utilizes the Bouc-Wen model to describe the nonlinearity and hysteretic behavior of the piezoelectric material. The governing electromechanical equation of motion for an inverted beam energy harvester is derived which includes piezoelectric hysteresis effect as a function of strain. Numerical simulations are presented to show how the piezoelectric material hysteresis changes the harvested electrical power for different excitation amplitudes and frequencies. This paper improves existing nonlinear electromechanical models to produce more accurate results by modeling piezoelectric material hysteresis.
On Phase Coupling of a Vortex-Induced Swing Sensor
Authors: Gong Ying , Peng Qianyi , Li Zhongjie 
Published: November 2023

Abstract
In recent years, the detection of climate and hydrology has become more and more important, and the related research of vortex-induced vibration has also been paid attention. Based on a vortex-induced swing structure that can realize flow direction sensing and energy harvesting, we study the phase coupling problems caused by structural size. In this paper, according to the research on the trajectory of the vortex-induced fluid-structure coupling motion, it is shown that a solid (e.g. cylinder) has the tendency of torsion under laminar impact. While the swing amplitude of the cylinder with a single bluff is low and unable to meet application requirements. Based on fluid-solid boundary layer theory, C shaped elastomer structure is designed to enhance torsional swing. The size of the cylinder and the C-shaped elastomer affects the frequency and phase of vortex-induced swing, and then influences the whole swing amplitude. We established a mathematical model for the phase study. In the experiment, by changing the ratio of the cylinder diameter to the width of the C-shaped elastomer, the swing amplitude characteristic under different conditions is obtained. Results show that when the sum of phase angle superposition is 2kπ + π, the phase coupling is suppressed. The width of C shaped elastomer is 25mm as the cylinder diameter is 18 when the suppression happens.
Determination of Material Parameters and FEM Simulation for the Development of a Design System for Shape Memory Springs
Authors: Hiekel Alexander , Hoffmann Fabian , Krieg Romina , Theiß Ralf , Pagel Kenny , Pelshenke Christian , Horn Simon , Mehrbakhsh Mehrdad , Drossel Welf-Guntram , Dültgen Peter 
Published: November 2023

Abstract
Including characteristic alloy parameters in the design process of shape memory springs is crucial to enhance the performance of the resulting actuator. In contrast to conventional spring steel, shape memory alloys (SMA) show a non-linear stress-strain curve based on a thermal- or stress-induced phase transformation. Substitute models obtained from linear approximations do not adequately represent these material properties. Consequently, the designed actuators are liable to oversizing without fully exploiting the potential strokes and forces. This paper shows an alternate system design method based on cause-effect relationships between the material parameters, the spring geometry, and the resulting actuator behaviour. To identify the relationships, FEM models of various SMA spring geometries, such as helical, shaft and wave springs, were implemented in the ANSYS Mechanical simulation software. Moreover, the springs were manufactured to validate the models using standardized test methods such as tensile-compression tests and DSC (Differential Scanning Calorimetry) measurements. These validated models form the basis to determine the cause effect-relationships via the Design of Experiment (DoE) method. Finally, discrete mathematical descriptions of the relationships are derived and implemented into a shape memory spring layout tool. The derived method achieves a substantially higher accuracy compared to linear substitute models. In addition, it is worth highlighting that the usage of the layout tool does not require special knowledge in thermo-mechanical simulation. Hence, it will be of particular interest for small and medium companies to access the technology more easily.
Econo-Finger: 3D Printed Soft Orthotic Finger With Embedded Strain Gauge and Actuated by Coiled Shape Memory Alloy Muscles
Authors: Miles Drew , Tadesse Yonas 
Published: November 2023

Abstract
Ischemic stroke is a deadly and debilitating medical event that leaves many people with motor disfunction. Post-stroke loss of hand functionality can be restored through powered hand orthosis. Artificial muscles like coiled shape memory alloy (SMA) can provide the necessary tension and pulling force needed to assist with flexion of the digits. Coiled SMA muscles have been implemented in several orthotic devices. One of the greatest obstacles in powered orthotic design is affordability. Leveraging inexpensive manufacturing processes like 3D printing can greatly minimize production and consumer cost and help customization. This would greatly bridge the price gap that exists between passive orthoses and smart feedback-controlled orthoses.
This work proposes an electrically powered single finger soft orthosis with embedded strain gauge made through a single step 3D printing approach. We utilized inexpensive coiled nickel titanium SMA muscles to assist in flexion of the index finger. Using an embedded strain gauge made from conductive thermoplastic polyurethane (CTPU), we can accurately monitor the flexion angle of the index finger. This precise data can be paired with electromyography (EMG) control to produce feedback-controlled movement. The expected fabrication cost of this orthotic finger is below $750, making it much cheaper than other smart powered orthoses currently available. We will show how the device responds to cyclic use under different input parameters. Using these responses, we will develop strategies to leverage the performance of the device for a variety of activities of daily life.
Antibacterial Properties of Snakeskin Inspired PDMS Surfaces Layered With Poly-DL-lactic Acid Nanosheet
Authors: Ibrahim Mohd Danial , Ananthan Alyssa Asong , Abang Mahmod Dayang Salyani , Awang Husaini Awang Ahmad Sallehin , Sing Ngieng Ngui , Nakano Shunsuke , Sunami Yuta , Barroy Pierre 
Published: November 2023

Abstract
The increment of sterilization resistant bacteria minimizes the effectiveness of disinfectants which leads researchers into studying other means in minimizing bacterial contamination on surfaces. Hence, this study plans to investigate surfaces with the ability to discourage bacterial adhesion and reduces the need for frequent sterilization. This study tested the feasibility of applying snakeskin inspired microstructures onto a polydimethylsiloxane (PDMS) surface to reduce bacterial adhesion and increase its antibacterial properties. In theory, the microstructure of snakeskin is smaller or about the same size as a bacterium making it unfeasible for bacterial adhesion. The embeddedelastomeric stamping method was used for the biomimicry of snakeskin onto PDMS surfaces. The replicated snakeskin and controlled (no microstructure) PDMS samples were layered with Poly-DL-lactic acid (PDLLA) nanosheet of different thickness. Then, the morphology of the surfaces was observed using a scanning electron microscope. The surface of the samples was tested with Staphylococcus aureus and Bacillus with compliance of the ISO 22196 standard to evaluate the antimicrobial activity. Our results revealed, surfaces with snakeskin microstructures displayed a 16% reduction in bacterial adhesion compared to flat PDMS. Whereas the presence of nanosheet does not significantly affect the adhesion of bacteria on the replicated snakeskin. These findings suggest that surfaces with the presence of snakeskin microstructures possess antibacterial property.
Annealed Pyrolytic Graphitic Carbon Electrodes for Piezoelectric Acoustic Nanoweb
Authors: Chytanya Chinnam Krishna , Sepehr Moeini Seyed , Tuti Simonetta , Lanzara Giulia 
Published: November 2023

Abstract
The primary challenge in realizing an ultimate lightweight and flexible acoustic sensing device is the electrode material. To obtain the best device performance expensive gold electrodes have been used in the literature due to the relatively higher electrical conductivity. In this paper we implement an annealed pyrolytic graphitic carbon on carbon fibers to form a low-cost highly performing porous electrode for acoustic applications. The electrode is prepared by using a 400-micron thick PMMA membrane electrospun on a unidirectional carbon fiber textile. The electrode is then used to form an acoustic sensor via a hybrid 3D printing-electrospinning-pyrolysis approach which allowed to deliver an overall flexible acoustic device. Preliminary results show a low noise level functional material with reasonably high electromechanical output to a wide range of acoustic frequencies. The higher sensitivity of the material with respect to the devices formed with continuous electrodes, is to be attributed to the porosity of the electrode material which enhances the vibrating air particles to interact with the interacting membrane directly and homogenously.
Investigation of the Thermal Heat Exchange Between NiTi-Wire Bundles and Airflow for Different Wire Arrangements
Authors: Welsch Felix , Kirsch Susanne-Marie , Louia Franziska , Seelecke Stefan , Motzki Paul 
Published: November 2023

Abstract
Nickel-Titanium (NiTi)-based shape memory alloys (SMAs) enable new sustainable and environmentally friendly solid-state heating and cooling technologies. Elastocaloric (EC) heat pump systems exploit superelastic SMAs as a non-volatile, inflammable, and non-global-warming refrigerant, in contrast to the well-established vapor compression technology. The high specific latent heat released or absorbed during mechanical loading or unloading of the SMA material leads to a high temperature change in the material. As a result of the small required work input to induce the phase transformation, a high coefficient of performance (COP) can be achieved by this technology. The potential of these alloys can be exploited through an adequate thermodynamic cycle, efficient mechanical system design, and choice of suited EC materials.
A fully functional continuous operating EC heat pump system based on SMA was developed and realized recently. To assist the design process of an optimized device with given performance and efficiency requirements, the air-cooling behavior of single wires and simple bundle arrangement has been analyzed, and intensive parameter studies on different airflow rates have been performed.
For optimizing the heat transfer using bundles, the influence of different angles of attack between the wire arrangement and the airflow is investigated, and the temperature development in the bundle, as well as the effects on the thermal performance, are presented in this work.
Thermomechanical Processing of NiTiCu Shape Memory Alloy From Button to Wire
Authors: Gantz Faith , Al Jabri Nehal , Worrell Dominique , Young Marcus L. , Palisoc Art 
Published: November 2023

Abstract
Shape memory alloys (SMA) are a lightweight and compact option for actuators because of their high energy density capacity and allowing the system weight to be reduced by a fraction of conventional actuators. An SMA processed into wire with a narrow hysteresis and great thermomechanical stability can ease integration into novel actuation designs. These designs can improve the thermomechanical response and reduce the energy usage, weight, and mechanical complexity of the system. Compositionally substituting Ni for Cu in the NiTi SMA system creates an SMA with these characteristics in comparison to binary NiTi SMAs. In this study, a set of NiTiCu SMA compositions were thermomechanically-processed using conventional methods such as rolling and drawing to produce plates, rods, and 0.50 mm diameter wire. Every processing step was characterized to monitor the evolution of microstructure and thermomechanical properties by using various microscopy, spectroscopy, and diffraction techniques. The NiTiCu wires were shape-set using a custom-made device to form small springs with dimensions specified to an actuating device within the reorientation mechanism of a CubeSat. Springs were made from NiTiCu wires and from commercially available NiTi wires, then thermomechanically cycled 50 times to train and compare the thermoelastic properties and actuation response.
Acoustic Meta-Structure Transmission Loss Characterization via an Impedance Tube and the Transfer Matrix Approach
Authors: Beals Matthew D. , Chavan Shantanu H. , Malladi Vijaya V. N. Sriram 
Published: November 2023

Abstract
This paper proposes a new meta-structure bandgap depth measurement method that considers energy absorption rather than discrete structural response. By applying measurement techniques previously reserved for acoustic property characterization, this novel method aims to characterize acoustic meta-structures by their transmission loss (TL). Transmission loss is the ratio of incident energy to transmitted energy from a structure. One extensively defined testing method for determining acoustic transmission loss involves using an impedance tube or a tube outfitted with transducers flush to its inside wall on either side of a sample holder, along with a source and termination on either end of the tube. Using the transfer matrix approach and transfer functions computed from the impedance tube transducers, the pressure and particle velocity at one point in space and time can be related to that of another point in space and time. In the end, a transfer matrix can be determined, which contains information about how much energy is absorbed, reflected, and transmitted by a structure over an entire range of frequencies. By outfitting an impedance tube to accept acoustic meta-structure samples, this same method can determine the transmission loss versus frequency exhibited by such a structure. This information can be used to directly observe and measure the band gap depth of an acoustic meta-structure.
Dynamic Mode Decomposition Approach for Estimating the Shape of a Cable
Authors: Chavan Yash Manik , Malladi Vijaya V. N. Sriram , Bae Jung Yun , Park Myoungkuk , Krishnan Manu 
Published: November 2023

Abstract
This study investigates the dynamic behavior of a flexible cable with heterogeneous stiffness using a data-driven approach. The study aims to develop accurate models that describe intricate structures with rigid or flexible components. To achieve this, reflective markers were attached to the cable at equal spacing and the motion was manually excited and captured using an 8 camera setup and OptiTrack’s Motive software.
Cable displacement data at marker locations were used as initial conditions for various Dynamic Mode Decomposition (DMD) models. The performance of the data-driven cable model is compared against the performance of the DMD modeling approach, fitting the dynamics of single- and multidegree-of-freedom systems with added white noise. In this work, the authors have considered using time delays and Wavelets-based DMD.
The study found that the wavelet-based DMD (WDMD) model was the most accurate method for reconstructing the response of the cable in the test cases. Researchers suggest that this data-driven approach can be applied to predict the dynamic behavior of nonlinear systems, with potential applications in civil engineering, aerospace, and robotics. Overall, this study presents a promising approach for developing accurate models of complex structures with rigid or flexible components. The findings of this study may be valuable in designing structures that can withstand dynamic loads and vibrations.