bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rearrangement of the Temperature Field in Flow Around a Bend
Authors: Eckert E. R. G. , Irvine T. F. 
Published: January 2022

Abstract
Measurements of the temperature and velocity field are reported for a specific duct geometry which bends the flow by 90 deg and simultaneously accelerates it to an average exit velocity which is twice the inlet velocity. The measurements demonstrate that the temperature field existing in a cross section upstream of the bend is considerably rearranged by the action of the secondary flow. The temperature field also influences the velocity field as observed in the exit cross section. A simple calculation method which allows a prediction of these effects in the core of the flow field is presented and good agreement to the results of the measurements is found. The importance of this flow rearrangement to various engineering applications, especially to the design of gas turbines, is discussed.
Present State and Future Outlook of the Free-Piston Engine
Authors: Huber R. 
Published: January 2022

Abstract
The first part of the paper gives a short description of the gasifier, type GS-34 gasifier, with diagrams showing the main operational factors versus gas pressure and stroke length. The present state of its application to ships, stationary plants, and locomotives is reviewed briefly. Details are given when running with a reduced number of gasifiers in service in a stationary power plant of 6000 kw (Cherbourg). In the second part the trend of future development is examined, especially with regard to an increase in power output per gasifier. The possibilities and limits of supercharging and after-burning are studied, as well as twinning of the gas-generators and increase of their size. The general relationship for similar engines but of different sizes is given. A gasifier with a 20-in. diesel bore is studied. Such an engine, supercharged, twinned, and with after-burning would produce 8000 to 10,000 hp on the turbine shaft per unit.
Time Domain Synthesis of Sampled-Data Control Systems
Authors: Jury E. I. , Semelka F. W. 
Published: January 2022

Abstract
This paper deals with the application of the modified z-transform to synthesis of sampled-data control systems. The applicability of the modified z-transform as an analysis tool has been demonstrated in recent publications. Currently, this transform method is being developed to reduce the process of synthesis of both sampled-data and continuous systems to systematic, straightforward numerical processes. In several recent papers [1, 2, 3] the z-transform has been applied to synthesis of sampled-data systems in both time and frequency domain methods. From these papers and their discussions, the need for the refinement in synthesis to include the continuous response characteristics is apparent. The synthesis procedure presented is a time domain technique which permits the designer to achieve control of the continuous behavior of the system. The desired characteristics are specified in terms of standard synthesis criteria, and from such specifications the required compensation transfer functions are determined.
Reinforced Concrete Barrier Modeling In-Series Impacts in LS-DYNA
Authors: Sharma Roshan , Silvestri Dobrovolny Chiara , Hurlebaus Stefan , Kiani Maysam 
Published: January 2022

Abstract
The design of longitudinal barriers using reinforced concrete is typical in roadside safety design. Roadside safety hardware such as bridge rails, median barriers, and transitions are designed to safely contain and redirect impacting vehicles without imposing any significant risks to the occupants. As full-scale crash tests of new designs are expensive and time-consuming, finite element modeling and simulation of the impact event is often involved. In LS-DYNA, one of the most popular software in roadside design, there are multiple material models for concrete modeling and there is no specific guideline on the selection of the concrete material model. This paper evaluates the behavior of material models MAT_CSCM_CONCRETE and MAT_RHT during the study of truck platoon implications. The concrete erosion, deflection, and failure mechanism of two consecutive tractor-van trailer impacts into the barrier FEA models were analyzed to select a representative material model for further study.
Tunable Enhanced Vibration Energy Harvester As a Power Module for Portable Electronics and IoT Sensors
Authors: Nguyen Hieu , Bardaweel Hamzeh 
Published: January 2022

Abstract
This article presents a novel, low-frequency, tunable, and wearable power module that can power portable electronic devices by harvesting power from human body motion. The device features a unique spring system that allows the power module to harvest at low-frequency range; ideal for integrating into daily human activities. The unique design of the power module allows for low-frequency specialization, i.e., less than 5 Hz. The spring system can be tuned into one of two modes. The optimum load resistance is determined to be 96 Ω. When shaken by hand and connected to a smartphone, the power module outputs a power of approximately 35 mW. The power module is handheld and has a small volume of roughly 3.8 × 7.6 × 17.8 cm3. An internal power management circuitry that can convert the AC output voltage from the harvester into a DC voltage is built and tested experimentally. In this work, the ability of the power module to utilize vibrations from human body motion in charging a smartphone is demonstrated.
Simulation of Spatters Sticking Phenomenon in Laser Powder Bed Fusion Process Using the Smoothed Particle Hydrodynamics Method
Authors: Meng Lingbin , Sun Tao , Dube Tejesh , Sagar Sugrim , Yang Xuehui , Zhang Jian , Zhang Jing 
Published: January 2022

Abstract
In this work, a smoothed particle hydrodynamics (SPH) method is developed to simulate the spattering phenomenon in the laser powder bed fusion (L-PBF) process. First, an experiment using the high-speed synchrotron X-ray full-field imaging is conducted to acquire in-situ images during the L-PBF process. Then, a scenario is selected from the X-ray image as a case study of the SPH model. In the case study, a particle is ejected and melted by the metal vapor, impacts with another particle, solidifies, and sticks to the other particle to form a rigid body. As a result, the trajectories of the two particles match well with the experimental observation. The evolution of velocity and temperature of the particle is extracted from the simulation for analysis. The SPH model can be a useful alternative to computational models of simulating the spattering phenomenon of L-PBF.
Design and Construction of a Spherical Mobile Robot Prototype for Monitoring Oil Palm Plantations
Authors: Roa Prada Sebastián 
Published: January 2022

Abstract
Colombia is the biggest producer of palm oil in Latin America. The production of palm oil alone makes up for 6% of the agricultural gross domestic product of the country. However, growing oil palm trees is a risky business since this kind of tree only starts producing its fruits when it reaches the age of three years, and during that time the trees are very prone to contract several diseases, which may completely damage the tree. The most common, and devastating, disease that can affect oil palm trees is the bud rot disease, which destroys the young tissue of the palms. Experts indicate that when the disease is detected in its early stages, a simple pruning of the affected area together with a chemical control may be enough to fight the disease. Therefore, there is a strong need for continuous monitoring of the trees. Some of the main challenges for the monitoring of oil palm plantations are the large areas that must be covered, the difficult environmental conditions with high temperatures and relative humidity, and the irregularities of the terrain. One way to make this monitoring task more cost effective, as compared to doing it only by means of human workers, is with the assistance of mobile robots. There are different kinds of mobile robots that have been used in precision agriculture applications such as tracked robots and wheeled robots. Although these robots offer several advantages such as simple mechanics and good payload capacities, in many cases they may not be the best choice, for example in very uneven or muddy terrain.
This work proposes the study, design and construction of a spherical robot, intended for remote monitoring of oil palm plantations. Spherical robots provide an interesting alternative for monitoring of plantations thanks to their excellent maneuverability and adaptability to various terrain conditions. Spherical robots can rotate in place to change direction, can move over muddy terrain and they can even float and move over water. They also have some disadvantages such as difficulties to pass over an obstacle and lower payload capacity.
This work was carried out in 4 stages, the first one was the selection of a locomotion architecture that adapts to the proposed design conditions. Then, the mathematical model of the robot was obtained, which allowed simulating the dynamic behavior of the robot and designing a control system to guarantee the stability needed for the guidance of the robot. Finally, the prototype was built and validated.
Vibration and Acoustic Crepitus Sensing Using Piezoelectric Accelerometers and Automated Signal Analysis
Authors: Roytman Gregory , Budavich Matthew , Pocius Judith D. , Faydenko Jocelyn , Muligano Dana , Cramer Gregory 
Published: January 2022

Abstract
The vibration and acoustic emissions produced within facet joints of the lumbar spine, known as crepitus, can be a potential biomarker to identify decreased joint functioning and the site of low back pain. Using piezoelectric accelerometers and a silicone “phantom” mechanical model we sought to identify the site of crepitus. Past analyses of these data with human observers have been too time consuming for eventual practical clinical application, and a more expedient algorithmic method of analysis is preferable. In this study the signal filtering and processing functions of MATLAB were harnessed to filter aberrant noise as well as determine the location (level and left or right side) from which crepitus originated during induced crepitus events in the phantom model (n = 30). Development of this automated method refined the definition of facet joint crepitus. The automated method was found to be as reliable and valid as assessment by human observers, and took significantly less time (p = 0.009). Future studies will assess the reliability of the automated method to detect this phenomenon in humans.
Thermophysical Properties of U-10Mo Monolithic Fuel
Authors: Ozaltun Hakan 
Published: January 2022

Abstract
Monolithic fuel is a candidate fuel form that is being considered for the conversion of high-performance research reactors. This plate-type fuel consists of a high-density, U-Mo fuel in a monolithic form that is sandwiched between zirconium diffusion barriers and encapsulated in an aluminum cladding. To date, many plates were irradiated with a satisfactory irradiation performance, demonstrating that the conceptual design works. The program is now moving to the qualification phase, a predecessor to the timely conversion of the target reactors. To qualify this fuel system, the program must show that the fuel plates have predictable behavior, meet the safety standards, and perform well in reactors. The requirement of a satisfactory irradiation performance under normal operating conditions is primarily demonstrated by a successful testing. To demonstrate that the fuel system has a predictable behavior, the several key material properties should be quantified accurately since these properties are needed to estimate the thermal and mechanical behavior of the fuel system. Although, there is a large set of thermophysical property data available for unirradiated material, the property data for irradiated fuel is scarce. Since irradiation causes drastic effects in material, a significant change in material properties occurs. Consequently, using representative degradation models becomes essential for accurate performance assessments. This work examines thermal conductivity of U-10Mo, by evaluating recent experimental data from the literature and available theoretical models. The study has discovered inconsistencies in the literature data, revealing that previously developed theoretical models fail to predict the thermal conductivity of irradiated fuel.
An Ultra-Low-Frequency Active Vertical Vibration Isolator With Horizontal Constraints for Absolute Gravimetry
Authors: Yao Jiamin , Zhuang Wei , Feng Jinyang , Zhao Yang , Wang Shaokai , Wu Shuqing , Fang Fang , Li Tianchu 
Published: January 2022

Abstract
Absolute gravimeters have been widely used as an important instrument in geological exploration and geophysics. To achieve a required measurement precision, it is necessary to integrate a vertical vibration isolator with ultra-low resonance frequency into the gravimeter. In this paper, an active vibration isolator designed on the basis of a BM-10 passive vibration isolation platform is presented. In the isolator, a seismometer placed next to the payload on the same plate outputs a voltage signal proportional to the payload’s velocity. According to this signal, a feedback circuit based on a PID controller controls two identical voice coil actuators to drive the platform synchronously. In this way, the vibration of the payload is suppressed. The BM-10 platform has 6-DOF passive vibration isolation originally, but its horizontal vibration isolation is proved unnecessary or even harmful in absolute gravimetry. Hence, two linear bushings are applied as a horizontal constraint to ensure that the payload only moves vertically in a straight line. Experiments show the resonance period of the isolator reaches approximately 88 s. In addition, the active vibration isolator has shown a much better performance for vibrations at low frequency than the passive isolator. In the future, the vibration isolator will be improved and then be integrated in the NIM-AGRb-1 atom-interferometry absolute gravimeter for the evaluation of its performance.
High Fidelity Human Modeling via Integration of Skeleton Tracking for Predictive HRC Collision Detection
Authors: Streitmatter Gabriel , Flowers Jared , Wiens Gloria 
Published: January 2022

Abstract
This paper develops a predictive collision detection algorithm for enhancing safety while respecting productivity in a Human Robot Collaborative (HRC) setting that operates on outputs from a Computer Vision (CV) environmental monitor. This prediction can trigger reactive and proactive robot action. The algorithm is designed to address two key challenges: 1) outputs from CV techniques are often highly noisy and incomplete due to occlusions and other factors, and 2) human tracking CV approaches typically provide a minimal set of points on the human. This noisy set of points must be augmented to define a high-fidelity model of the human’s predicted spatial and temporal occupancy. A filter is applied to decrease sensitivity of the algorithm to errors in the CV predictions. Kinematics of the human are leveraged to infer a full model of the human from a set of, at most, 18 points, and transform them into a point cloud occupying the swept volume of the human’s motion. This form can then quickly be compared with a compatible robot model for collision detection. Timed tests show that creation of human and robot models, and the subsequent collision check occurs in less than 30 ms on average, making this algorithm real-time capable.
Drying of a Fully Saturated Porous Medium With Excess Water Layers - A Numerical Study
Authors: Asar Munevver E. , Yagoobi Jamal S. 
Published: January 2022

Abstract
Drying of moist porous media can be very energy inefficient. For example, in the pulp and paper industry, paper drying consumes more than two-thirds of the total energy used in paper machine. Novel drying technologies can decrease the energy used for drying and lessen the manufacturing processes’ carbon footprint. Developing next generation drying technologies to dry moist porous media may require understanding of removing moisture from fully saturated porous material with excess water. During papermaking, dry paper is fully saturated with in a water mixture that contains additional “excess water” before reaching the pressing section of a paper machine.
This paper provides a fundamental understanding of heat and mass transfer in fully saturated porous medium with excess water. For this purpose, a theoretical drying model is developed where the porous medium corresponds to paper and is assumed to be sandwiched between two excess-water layers (bottom and top). The thickness of each water layer is calculated, based on local temperature and total moisture content. The numerical model is transient and one-dimensional in space in thickness direction. This paper demonstrates the governing equations, boundary conditions, and results when the saturated porous medium with water layers is heated from one (bottom) side. Moisture and temperature profiles are estimated in the thickness direction of the porous medium as it dries. Results show that initial drying is rapid, due to the drying of the top water layer. Then, the moisture from the bottom water layer penetrates the porous medium, as the porous medium becomes slightly unsaturated due to evaporation at its top surface exposed to ambient air. When the bottom water layer is dried up, the porous media starts losing its moisture more significantly than in the previous stages, as expected.
Multi-Objective Thermal Optimization of a Nanofluid-Cooled Rectangular Microchannel Heat Sink Using Genetic Algorithm: A Comparative Study
Authors: Fazeli Hamid 
Published: January 2022

Abstract
The use of nanofluids as coolant fluid in the microchannel heat sink (MCHS) is an effective technique for the improvement of thermal performance in electronic devices. A comparative study is performed with the help of a multi-objective genetic algorithm (MOGA) to find the optimal geometric variables of the MCHS and choose the appropriate nanofluid and its optimal characteristics. For that purpose, four practical nanofluids, including Al2O3-water, Cu-water, SiO2-water, and carbon nanotube (CNT)-water, are thoroughly investigated. Simultaneously minimization of the total thermal resistance and pumping power consumption are taken into account as the optimization goal, and the MOGA is employed to achieve the optimal solution. To check the accuracy of the thermal resistance modeling and assessing the optimization algorithm, several case studies with a different number of optimization variables are defined to investigate the capability of the algorithm in finding the optimal microchannel design variables and choosing the suitable nanofluid. The optimization variables consist of the channel aspect and wall ratios, base thickness, volume nanoparticle concentration, diameter, and volume flow rate. Compared to other nanofluids, CNT provides better thermal performance. Increasing the concentration of nanoparticles enhances thermal performance, which can also be achieved through the reduction of nanoparticle diameter. Results of the considered case studies also show that considering more design variables through the optimization procedure, better thermal performance is achievable.
Control Temperature of the Air Conditioning System of a Vessel From Exergoeconomic Analysis
Authors: Barreto Deibys , Fajardo Juan , Berrio Julián , Torres Rosa , Gordon Yimy , Vidal Carlos 
Published: January 2022

Abstract
In this work the air conditioning system of a 93 m long and 14 m wide vessel with 4081 refrigerated m3 distributed in 51 premises is studied. In which energy, exergetic and exergoeconomic analyzes were carried out for control temperatures between 20 and 27 ° C and 50% relative humidity, with outdoor air conditions of 35 ° C and 70% relative humidity. For the vessel, the thermal load is calculated with an adaptation of the ASHRAE CLDT / SCL / CLF (cooling load temperature difference/cooling load factor/solar cooling load factor) methodology and the ISO 7547 standard. Thermal load contributors taken into account for the study were heat transfer through walls, ceilings, and glass in addition to gains from people, lighting, and Appliances. Transmission through walls and ceilings represents 33% of the thermal load, followed by glass with 18% and power equipment with 15%, the last three sources of thermal load generation are Appliances (12%), people (12%) and lighting (10%). For each degree centigrade of the control temperature, the thermal load is reduced by 2.4 and 1.1%, respectively, as determined by the ASHRAE and ISO methodologies. Similarly, the destruction of exergy is reduced by 4.16% for each degree Celsius that the control temperature is increased. An indicator is proposed to calculate the cost of generation of cooling load per unit volume and exergy of the thermal load from which it is obtained that the higher the control temperature, the lower the value of the cost of generation of the cooling load. From the exergoeconomic analysis, it is highlighted that the destruction of exergy is the main factor in the increase in system costs. Increases in exergy destruction increase the value of the indicator of cooling load generation costs per volume and unit of heat load exergy. For each degree Celsius that the control temperature is reduced, the cost of generation of cooling load per volume and unit of exergy of thermal load increases on average 0.35%.
Spectral Correlation Method for Fatigue Crack Detection Based on Nonlinearly Mixed Ultrasonic Waves
Authors: Sampath Santhakumar , Sohn Hoon 
Published: January 2022

Abstract
Recent developments in the nonlinear ultrasonic wave mixing method have enabled its use in detecting early-stage fatigue cracks. In this method, two input waves at distinct frequencies are applied to a structure with a fatigue crack (i.e., a nonlinear structure). The interaction between these waves gives rise to nonlinearly mixed harmonic components at the sum and difference of the input components. However, the amplitude of the mixed harmonic components generated by the fatigue crack becomes weak in a noisy environment. To overcome this issue, the conventional power spectrum method is used to extract the nonlinear components; however, it is unsuitable for analyzing nonlinear and nonstationary signals. This study presents an advanced signal processing method, called the spectral correlation method, to overcome this problem. The proposed method considers not only the mixed harmonic components in ultrasonic waves, but also the spectral correlation between these components. The uniqueness of the proposed method lies in the following: (1) a single transducer is used, instead of two individual transducers, to generate two input Lamb waves sequentially, (2) the spectral correlation of the mixed harmonic components is insensitive to noise components; (3) tone burst inputs are used as in spectral correlation, and a good contrast between intact and fatigue crack conditions is obtained when compared with the sinusoidal inputs, (4) the mixed components extracted from the spectral correlation method are more reliable than those obtained using conventional methods, and (5) the proposed approach can be applied to detect fatigue cracks. A theoretical model is presented to establish a relationship between the spectral correlation coefficient and the quadratic nonlinearity parameter. Experiments were conducted on aluminum plate specimens with fatigue cracks to validate the performance of the spectral correlation method. The experimental results showed that the nonlinearly mixed harmonic component extracted using our method is more effective for fatigue crack detection than that extracted using the conventional power spectrum method.