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    Advancements in form-stabilized phase change materials: stabilization mechanisms, multifunctionalities, and applications - A Comprehensive Review
    (Elsevier, 2024-04) Yazdani McCord, Roza; Baniasadi, Hossein; Department of Mechanical Engineering; Department of Chemical and Metallurgical Engineering; Energy Conversion and Systems; Polymer Synthesis Technology
    Phase change materials (PCMs) possess remarkable properties that make them highly attractive for thermal energy storage and regulation purposes. Their ability to store energy in the form of latent heat while maintaining a nearly constant temperature has led to growing interest in their practical applications. However, a significant challenge in utilizing PCMs lies in their susceptibility to leakage and fluidity in the melt state. Therefore, it becomes imperative to develop effective methods to create leakage-free form-stabilized PCMs, enabling their widespread use in various industries. In this review, we comprehensively evaluate the advantages and disadvantages of different stabilization methods by summarizing the key research advancements in this field. We delve into the effectiveness of the various techniques in mitigating leakage issues and enhancing the overall performance of form-stabilized PCMs. Furthermore, we present the multifunctionalities that form-stabilized PCMs can offer, including self-healing, self-cleaning, fire-retardancy, and electrical and thermal conductivities. Moreover, we explore the diverse application areas of form-stabilized PCMs, including solar energy storage, buildings, textiles, biomedical, and electronics. These explorations promise advancements in energy efficiency, thermal comfort, and sustainable design. This review aims to shed light on the potential of form-stabilized PCMs in revolutionizing various sectors and contributing to a greener and more energy-conscious future.
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    PSO-Based Predictive PID-Backstepping Controller Design for the Course-Keeping of Ships
    (MDPI AG, 2024-02) Lin, Bowen; Zheng, Mao; Han, Bing; Chu, Xiumin; Zhang, MY; Zhou, Haiming; Ding, Shigan; Wu, Hao; Zhang, Kehao; Department of Mechanical Engineering; Marine and Arctic Technology; Wuhan University of Technology; National Engineering Research Center of Ship & Shipping Control System
    Ship course-keeping control is of great significance to both navigation efficiency and safety. Nevertheless, the complex navigational conditions, unknown time-varying environmental disturbances, and complex dynamic characteristics of ships pose great difficulties for ship course-keeping. Thus, a PSO-based predictive PID-backstepping (P-PB) controller is proposed in this paper to realize the efficient and rapid course-keeping of ships. The proposed controller takes the ship’s target course, current course, yawing speed, as well as predictive motion parameters into consideration. In the design of the proposed controller, the PID controller is improved by introducing predictive control. Then, the improved controller is combined with a backstepping controller to balance the efficiency and stability of the control. Subsequently, the parameters in the proposed course-keeping controller are optimized by utilizing Particle Swarm Optimization (PSO), which can adaptively adjust the value of parameters in various scenarios, and thus further increase its efficiency. Finally, the improved controller is validated by carrying out simulation tests in various scenarios. The results show that it improves the course-keeping error and time-response specification by 4.19% and 9.71% on average, respectively, which can efficiently achieve the course-keeping of ships under various scenarios.
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    Awareness increases acceptance and willingness to pay for low-carbon fuels amongst marine passengers
    (Elsevier, 2024-02-15) Nyári, Judit; Toldy, Árpád I.; Järvinen, Mika; Santasalo-Aarnio, Annukka; Department of Mechanical Engineering; Energy Conversion and Systems
    One of the main applications discussed in decarbonising the marine sector is via alternative fuels, such as methanol and ammonia, produced from renewable hydrogen. These alternative, low-carbon fuels often come with increased prices and operational expenses for the vessel operators, which are ultimately reflected in the passengers' costs. Therefore, it is important to assess passengers' familiarity with expressions linked to decarbonisation and their willingness to pay this ‘green premium’ for alternative fuels. To assess these, we ran a survey-based study and collected close to 2000 answers through different channels from marine passengers, specifically from those travelling in the Northern European region on roll-on/roll-off passenger (RoPax) vessels. We found that most of the passengers prioritise environmental friendliness in marine fuels and are concerned about environmental issues. However, there seems to be a lack of knowledge about fuels and fuel technologies. Familiarity with certain alternative fuel-related expressions results in a more positive view of them. The observed willingness to pay is affected by the level of education, income, and place of residence, in addition to the level of concern about environmental issues, frequency of travel and spending on trips. Close to 80% of passengers are willing to increase their spending if the vessel is powered by a low-carbon, alternative fuel. As the results indicate that the more passengers know about alternative fuels and their benefits, the more willing they are to pay for them, it is recommended that RoPax operators invest in educating them.
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    Improvements in Rock Mass Description for Stope Design by Geophysical and Geochemical Methods
    (MDPI AG, 2024-02) Rinne, M; Janiszewski, M; Pontow, S; Uotinen, L; Kiuru, R; Kangas, L; Laine, I; Leveinen, J; Department of Civil Engineering; Mineral Based Materials and Mechanics; Mineral Based Materials and Mechanics
    Stope design is an important part of mine planning, and it aims to balance ore recovery, ore dilution, and production costs without compromising the safety aspects. This paper summarizes the main results from the research, which aims to introduce new techniques to describe the ore body and surrounding rock mass at the tunnel face prior to stope excavation. The research comprises a literature review and a survey among mining professionals to assess current stope design practices. The study identifies geotechnical data, software improvements, and integration of design into mine planning as the most critical areas for improvement. The empirical part of the study proposes new techniques for fast data acquisition. The laser-induced breakdown spectrometry (LIBS) technique is developed for measurements at the tunnel face and from core boxes to provide mineralogical and geometallurgical data. Ground-penetrating radar (GPR) studies are conducted to improve discontinuity characterization, and rapid photogrammetric methods are proposed for efficient tunnel geometry characterization. The techniques discussed in this paper already have many industrial applications. This study reveals their potential to be adopted and further developed to serve ore and rock mass characterization for stope design.
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    Re:Urbia - lähiöiden kehityssuunnat ja tulevaisuus, mitä pitäisi tehdä
    (Geographical Society of Finland, 2024-02-06) Joutsiniemi, Anssi; Vaattovaara, Mari; Arkkitehtuurin laitos; Rakennetun ympäristön laitos; University of Helsinki
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    Hot In-Place Recycled Asphalt Mixtures : RAP Analysis, Compaction Characteristics and Field Evaluation
    (MDPI AG, 2024-02) Wang, Teng; Zhao, Xin; Zheng, Lele; Mao, Chengxin; Wang, Li; Falchetto, Augusto Cannone; Guo, Dedong; Department of Civil Engineering; Mineral Based Materials and Mechanics; Chang'an University; Shaanxi Transportation Planning and Design Institute Co., Ltd.; Shandong Sanjian Group Co., Ltd.; Shandong Jiaotong University
    The substantial accumulation of reclaimed asphalt pavement (RAP) poses a pressing issue in road construction. The hot in-place recycling (HIR) technique has garnered widespread attention due to its high recycling rates of RAP and minimal environmental hazards. This study focuses on the RAP analysis, compaction characteristics, and field evaluation of hot in-place recycled asphalt pavements (HIRAP). Firstly, a novel test method of RAP analysis was proposed to evaluate the suitability of RAP. Subsequently, compaction tests reveal the compaction characteristics of hot in-place recycled asphalt mixture (HIRAM). Finally, the field performance of HIRAP was assessed. The research findings indicate that the RAP analysis method can accurately characterize the status of RAP. Increasing the RAP temperature improves the compaction characteristics of HIRAM. The field tests show that using HIR technology improves the performance of the pavement, in particular with a compaction of 99.7%. This study will establish a theoretical foundation for further promoting the HIR technique.
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    Developing thermal prediction models for the elderly under temperature step changes
    (Elsevier BV, 2023-11-01) Zhou, Shan; Li, Baizhan; Du, Chenqiu; Yao, Runming; Ouyang, Linyuan; Zhou, Haixia; Kosonen, Risto; Melikov, Arsen Krikor; Shang, Liangyue; Liu, Hong; Department of Mechanical Engineering; Energy Conversion and Systems; Chongqing University; Technical University of Denmark
    Daily transitions between indoor and outdoor environments involving temperature step changes have been extensively studied in young people, but little attention has been given to age-related differences and the development of thermal prediction models specifically for the elderly. To address this knowledge gap, a study was conducted in a climate chamber using warm-neutral-warm experimental sessions. Twenty-four elderly participants were selected from volunteers who met the health and body shape requirements. Thermal sensation vote (TSV) and mean skin temperature (MST) responses of the elderly were collected and analyzed. The results demonstrate that temperature step changes (3–9 °C) and neutral thermal experiences significantly influence the thermal responses of the elderly. Compared to the young, the elderly exhibit lower TSV, lower MST, lower skin heat loss, and different associations between TSV and skin heat loss. Leveraging these age-related differences, an MST prediction model was established for the elderly. The predicted MST can also serve as an input for the TSV prediction model established in this study. The TSV prediction model is based on skin heat loss and applicable to both transient and steady-state conditions. This study introduces a new approach for predicting the thermal responses of the elderly and enhances understanding of age-related differences in thermal responses.
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    Scaling ice-induced vibrations by combining replica modeling and preservation of kinematics
    (Elsevier, 2024-04) Hammer, Tim C.; Puolakka, Otto; Hendrikse, Hayo; Department of Mechanical Engineering; Aalto Ice Tank
    A modeling approach to simulate ice-induced vibrations of vertically sided offshore structures in ice tank experiments is presented. The technique combines replica modeling with the preservation of kinematics during ice-structure interaction. The technique was chosen based on the theoretical understanding that ice-induced vibrations are caused by an energy exchange between the structure and the ice. The mechanism is controlled by primarily four aspects: the kinematics during ice-structure interaction, the degree to which the ice can resist higher loading at low velocities prior to failure (velocity effect), the existence of a transition speed from ductile-to-brittle failure, and the mean ice load level. A model ice type which resulted in a velocity effect and provided a transition speed comparable to that of sea ice was developed and used during ice tank experiments. A scaling factor, derived from the comparison between the mean brittle crushing ice load of the full-scale event and the in-situ measured mean brittle crushing model ice load, was applied to scale structure properties of a numerical model. This model was implemented during real-time hybrid simulations in model ice to preserve kinematics during the ice-structure interaction. To verify the proposed scaling approach, rigid indenter experiments covering velocities from 0.1 mm s−1 to 500 mm s−1 and dynamic ice-induced vibration experiments of structures with varying aspect ratios (8 and 12) and shapes (cylindrical and rectangular) were conducted. Neither the aspect ratio nor shape appeared to influence the development of ice-induced vibrations significantly. The approach was qualitatively validated by reproducing full-scale ice-induced vibrations as experienced by the Molikpaq platform and Norströmsgrund lighthouse.
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    A viscous investigation on the hydrodynamic coefficients and wave loads under the interaction of side-by-side cylinders in regular waves
    (Elsevier Ltd, 2024-04-01) Jiang, Zongyu; Li, Fang; Tavakoli, Sasan; Kujala, Pentti; Suominen, Mikko; Hirdaris, Spyros; Department of Mechanical Engineering; Marine and Arctic Technology
    The paper introduces a two-dimensional Reynolds-Averaged Navier-Stokes Computational Fluid Dynamics (RANS CFD) model to investigate the effects of adjacently floating bodies on the hydrodynamic coefficients and wave loads acting on these bodies. The analysis considers two square cylinders with a narrow gap in way of the free water surface. The physical significance of subsections of the hydrodynamic coefficient matrix becomes evident when comparing coefficients obtained from oscillating-oscillating versus oscillating-fixed models. This understanding is significant, particularly in applications where only specific portions of the hydrodynamic coefficient matrix are utilized, such as in ship-ice collision scenarios (Jiang et al., 2023a). The correlation between wave loads and wave elevations reveals that the sway force and roll moment are associated with the disparity in wave elevation at both sides of each cylinder, while heave forces correlate with the averaged wave elevation on both sides of each cylinder. It is concluded that hydrodynamic interactions are sensitive to the displacement of a floater and accordingly can dominate added mass and damping effects.
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    A novel personal comfort system for older adults in hot conditions : Design, modelling, and performance
    (Elsevier BV, 2024-01-15) Younes, Jaafar; Chen, Minzhou; Ghali, Kamel; Kosonen, R; Melikov, Arsen Krikor; Kilpeläinen, S; Ghaddar, Nesreen; Department of Mechanical Engineering; Energy Conversion and Systems; American University of Beirut; Technical University of Denmark
    This study introduces a novel personal comfort system aimed at establishing a relatively uniform thermal microclimate around the body to meet the thermal needs of seated elderly individuals under hot conditions. The system integrates cool air supply vents into a chair to provide thermal comfort by i) generating upward airflow by colliding jets to disperse cool air across the upper body; and ii) releasing air flow targeting the lower body by relying on buoyancy for air confinement. A computational fluid dynamic model was developed to predict the flow and thermal fields around the occupant who is seated on a chair equipped with the proposed system. The model was experimentally validated in a climatic chamber using a thermal manikin. An elderly bioheat and thermal sensation models were used to predict skin temperatures and corresponding sensation of elderly users. The microclimate was assessed in terms of effective confinement of cool air around users and improvement in elderly thermal sensation. At a total chair supply flow of 17 l/s, microclimate air confinement was attained. At 29 °C room temperature, the proposed system lowered the mean skin temperature from 34.15 °C to 33.33 °C and improved the whole-body TS, which decreased from slightly warm to neutral. At 33 °C room temperature, the mean skin temperature decreased from 35.6 °C to 33.99 °C and the sensation improved, decreasing from above warm to below slightly warm.
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    Additive manufacturing of self-sensing parts through material extrusion
    (Taylor & Francis, 2024-02-28) Akmal, Jan Sher; Salmi, Mika; Department of Mechanical Engineering; Materials to Products
    The objective of this study is to develop and evaluate self-sensing capabilities in additively manufactured parts by embedding conductive elements that are copper and continuous carbon fiber. Two sets of test specimen were manufactured using a custom g-code on material extrusion-based Anisoprint A4 machine. Each set contained copper and continuous carbon fiber in an amorphous thermoplastic matrix. A tailor-made test setup was developed by improvising the American Society for Testing and Materials (ASTM D790) three-point loading system. Electrical resistance measurements were conducted under flexural loads to evaluate the self-sensing capability of each test specimen. The results confirmed that material extrusion technology can allow production of self-sensing parts. The electrical resistance increases linearly (Sensing tolerance <±2.6%, R^2>93.8% p-value < 0.005), establishing a strong correlation with applied force and strain. The work allows for creating smart parts that can facilitate big data collection, analysis, and evidence-based decision-making for condition monitoring and preventive maintenance needed for Industry 4.0.
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    Achieving social routing via navigation apps : User acceptance of travel time sacrifice
    (Elsevier Ltd, 2024-03) Vosough, Shaghayegh; Roncoli, Claudio; Department of Built Environment; Planning and Transportation
    Trip information and navigation systems are expected to become key components of future traffic management strategies, which, if properly exploited, may contribute to the mitigation of car usage externalities. In this study, we investigate social routing recommendations, which could be associated with nudges, and delivered via a navigation app, aiming at promoting sustainable routing behavior, where some drivers are asked to take longer routes and make travel time sacrifices (TTS). In particular, we propose a framework including data collection and behavioral modeling to identify the impacts of various types of information delivered to drivers, goals of the detour, and personal characteristics on drivers’ TTS behavior. The methodology includes stated choice and revealed choice experiments in two European cities, Amsterdam and Helsinki, and a mixed ordered-response logit model to provide insights into TTS behavior. Our analyses show that delivering different information and nudges results in different levels of TTS. However, regardless of the goal of the detour, offering incentives to drivers enables achieving a higher level of TTS. Comparing the stated and revealed data, regarding TTS and compliance rate, also clarifies significant differences between these two types of data.
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    DIC Analyses and Parameter Calibration of a Strain Aging Sensitive Ductile Cast Iron
    (Academie des Sciences, 2024) Valmalle, Malo; Widell, Kim; Ilola, Risto; Bossuyt, Sven; Department of Mechanical Engineering; Materials to Products; Materials to Products; Aalto University
    In the present work, the mechanical response of strain aging sensitive ductile cast iron was studied when subjected to uniaxial tension in temperatures ranging from 20°C up to 300°C. Digital Image Correlation (DIC) was used to measure the strain localization patterns due to dynamic strain aging. A constitutive law based on the Kubin–Estrin–McCormick model (KEMC) was used to model the behavior of the ductile cast iron in temperatures ranging from 20° up to 300°. The displacement fields were successfully measured and the strain localization patterns were observed. These measurements were employed to calibrate the parameters of the constitutive law. Numerical simulations are shown to be in agreement with experimental measurements at the macroscopic scale.
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    Dreaming the wrong dream : An exploratory case study of a policy change toward sustainable urban development in a medium-sized Chinese city
    (Wiley-Blackwell, 2024) Song, Yun; de Jong, Martin; Stead, Dominic; Yang, Wei; Wang, Biyue; Department of Built Environment; Planning and Transportation; Erasmus University Rotterdam; Fudan University; Northeastern University China; Delft University of Technology
    Sustainable urban transformation has become a mantra for Chinese cities. While most studies focus on sustainable urbanization in megacities, the far larger number of medium-sized cities is understudied, although the latter face more severe urban problems. This article develops a framework for examining policy change in sustainable urban development initiated at the central level and reactions, tensions, and implementation issues emerging at the local level. It focuses on an in-depth case study of the challenges in realizing a transition from quantity-oriented pro-growth policies to sustainable quality-oriented ones in a medium-sized Chinese city. We find that there is evidence of changes in long-term values and goals toward sustainability at the levels of both central and local government, but also great inconsistency between goals on paper and policy implementation in practice. Sustainability in urban development is much harder to realize as local officials see urban development as a major means to maintain local economic growth, which can be separated from other issues in ecological preservation. The article concludes with a roadmap for future studies focusing on medium-sized cities, especially indicating how narratives on sustainable urban development hide from view financial and environmental risks generated by the actual implementation of the dominant aggressive urban pro-growth model.
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    Detecting changes in price-sensitivity of household electricity consumption : The impact of the global energy crisis on implicit demand response behavior of Finnish detached households
    (Elsevier Science Inc., 2024-03-01) Einolander, Johannes; Kiviaho, Annamari; Lahdelma, Risto; Department of Mechanical Engineering; Department of Mathematics and Systems Analysis; Energy Conversion and Systems; Operations Research and Systems Analysis
    The energy transition combined with the ongoing global energy crisis and soaring inflation has pushed household electricity prices to all-time high levels. The year 2022 was especially rough for customers due to significant electricity price increases, leading to, for instance, a fall in the European consumer confidence index to a new all-time low. When dealing with very high electricity prices, the only things household can do to reduce their utility bills is to reduce consumption, invest in self-generation, or change to a time-based electricity contract and shift consumption to cheaper times. In this study, we present a methodology for analysis of changes in customer electricity use behavior and price-sensitivity based on smart electricity meter data, correlation analysis and the k-means clustering algorithm. Electricity meter data is further used to cluster customers into different primary heating type groups to analyze whether there exist behavioral change differences between these groups. As a case study we utilize these methods to investigate the impact of the global energy crisis and rapidly risen electricity prices of 2022 on the price-sensitivity of Finnish detached house electricity use. Based on our results, almost a third of the analyzed households had a statistically significant increase in implicit demand response behavior from January to December of 2022. The largest shares of households with a statistically significant increase in price-sensitivity were in night-time water heating, oil, and ground-source heating groups.
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    A voyage-level ship performance modelling approach for the simulation of the Finnish-Swedish winter navigation system
    (Elsevier Ltd, 2024-03-01) Kulkarni, Ketki; Li, Fang; Kondratenko, Aleksander A.; Kujala, Pentti; Department of Mechanical Engineering; Marine and Arctic Technology
    The Finnish-Swedish winter navigation system plays an essential role in logistics to the ports surrounded by frozen sea in winter. Coordination of icebreakers is crucial to guarantee sufficient transit speed of merchant ships and minimize the waiting time. Simulation of the winter navigation system provides the opportunity to optimize the system performance and help the planning of future icebreaker fleets. For simulation, estimation of ship performance, such as the actual speed in ice, is essential. Calculation methods to estimate ship performance in such contexts are typically required to be of simple form without the need for heavy computation. Existing ship performance models embedded in route optimization algorithms and winter navigation simulations in the literature are often oversimplified. This paper proposes a systematic ship performance modelling approach which accounts for a wide range of parameters, such as ice condition and parameters, power variation and icebreaker assistance. The approach is validated against real ship voyages. The proposed approach is implemented into a simulation model which simulates the operation of merchant ships and icebreakers on the Baltic Sea. Analyses are conducted on the system level in terms of the waiting time of merchant ships needed for icebreakers as well as the energy consumption.
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    Thickness-independent fracture in columnar freshwater ice : An experimental study
    (Elsevier Ltd, 2024-03-08) Gharamti, I. E.; Ahmad, W.; Puolakka, O.; Tuhkuri, J.; Department of Mechanical Engineering; Marine and Arctic Technology; Materials to Products; Aalto Ice Tank
    Experiments on columnar freshwater ice indicated that there is no detected effect of the ice thickness on the fracture behavior of columnar freshwater S2 ice. The influence of thickness was studied using large laboratory-grown samples. Two series of Mode I fracture tests were carried out using deeply edge-cracked 3-by-6-metre rectangular plates loaded monotonically at 1…100 μm/s. The ice was warm (above −0.5 °C), and the ice thickness varied in the range 10–40 cm. This paper analyzes the second series of tests and compares the results with the first series tests; the analysis of the latter was published in Gharamti et al. (2021) [2,3,4]. The viscoelastic fictitious crack model (VFCM) was applied to analyze the data and calculate the crack profile, fracture energy and the process zone size. The thickness affected only and linearly the values of the measured loads with no influence on the fracture properties: the apparent fracture toughness, fracture energy, crack opening displacements, notch sensitivity and process zone size.
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    A finite element simulation approach for glued-laminated timber beams using continuum-damage model and sequentially linear analysis
    (Elsevier BV, 2024-04-01) Jaaranen, Joonas; Fink, Gerhard; Department of Civil Engineering; Structures – Structural Engineering, Mechanics and Computation
    Glued-laminated timber (GLT) is an efficient and renewable material with potential to enhance sustainability in construction, but its potential has been partly hindered by relatively large uncertainty related to its strength. Previous research indicate that by linking information from the grading process to the GLT fabrication more reliable GLT beams could be made. To this end, this paper represents a finite element based modelling approach combining a continuum damage model with sequentially linear analysis that is suitable for simulation of the bending stiffness and strength of GLT beams. The model has been implemented in Matlab and can be easily integrated into different parametric simulation workflows. Based on validation against 36 experimentally tested GLT beams, the model can predict bending stiffness with high accuracy and provides reasonably accurate predictions for bending strength. The model is also capable of producing qualitatively realistic fracture patterns of GLT beams. The mesh-size study suggests that the best agreement for bending strength with test data is obtained with a sparse mesh, which is discussed in detail. The model is considered suitable for follow-up studies involving the optimization of GLT beam layups.
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    Effect of Biochar Type and Amendment Rates on Soil Physicochemical Properties: Potential Application in Bioengineered Structures
    (ASTM International, 2024-01-29) Hussain, Rojimul; Kumar, Himanshu; Bordoloi, Sanandam; Jaykumar, Swathylakshmi; Salim, Salih; Garg, Ankit; Ravi, Karangat; Sarmah, Ajit K.; Gogoi, Nirmali; Sreedeep, Sekharan; Department of Civil Engineering; Structures – Structural Engineering, Mechanics and Computation; Indian Institute of Technology Guwahati; Hong Kong University of Science and Technology; Viswajyothi College of Engineering and Technology; Shantou University; University of Auckland; Tezpur University
    Biochar has recently gained attention as a potential soil amendment for its usage in bioengineered structures, e.g., landfill cover system, green slopes, green corridor, etc., that usually comprises compacted soil with vegetation. In literature, many studies have explored the effect of biochar sourced from plant (agri-residues, wood)- and animal-based biomass on physicochemical properties of soil suitable for agricultural application. However, systematic study rarely has been conducted for soil suitable for bioengineered structures, and contradictory results have been reported. The objective of the present study is to explore the effects of biochar produced from different feedstock types (poultry litter, water hyacinth, and sawdust) on physicochemical properties of soil for bioengineered structures application. The results revealed that the amendment of biochar increased the liquid limit (14–52 %), plastic limit (PL, 2–66 %), optimum moisture content (OMC, 4–50 %), pH (29–59 %), cation exchange capacity (20–428 %), and water absorption capacity (12–94 %), whereas it decreased the maximum dry density (7–17 %), specific gravity (3–17 %), and shrinkage area ratio (SAR, 22–57 %) of the soil. Among the different biochar types tested, water hyacinth biochar (WHB) exhibited the highest increase in PL, OMC, and pH, and decrease in specific gravity and SAR of the soil after amendment, whereas poultry litter biochar showed the lowest variation of the same. These changes in the soil physicochemical properties after biochar amendment are likely attributed to the presence of intrapores and active chemicals in biochar, which are highly dependent on feedstock types. The findings of the present study could be useful in understanding the hydro-mechanical and plant interaction of biochar-amended soil (BAS), and potential implementation of BAS in bioengineered structures.
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    Comparing positioning accuracy of mobile laser scanning systems under a forest canopy
    (Elsevier, 2024-06) Muhojoki, Jesse; Hakala, Teemu; Kukko, Antero; Kaartinen, Harri; Hyyppä, Juha; Department of Built Environment; MeMo
    In this paper, we compare the positioning accuracy of commercial, mobile laser scanning systems operating under a forest canopy. The accuracy was evaluated on a 800-m-long positioning track, using tree locations from both a traditional field reference, collected with total station, and a high-density airborne laser scanning (ALS) system as a reference. Tree locations were used since mobile lasers are studied for automation of field reference for forest inventory and location of individual trees with high accuracy is required. We also developed a novel method for evaluating the ground level around the trees, as it not only affects the z-coordinate, but the horizontal position as well if the tree is tilted. In addition to the accuracy that could only be evaluated for systems equipped with a GNSS receiver, we evaluate the consistency of laser scanning systems by registering the tree locations extracted from the mobile systems to both the field reference and ALS. We demonstrated that the high-density ALS has similar accuracy (RMSE of approximately 6 cm) and precision as the total station field reference, while being much faster to collect. Furthermore, the completeness of the high-density ALS was over 80 %, which is more than enough to register the other methods to it in a robust manner, providing a global position for laser scanners without an inherit way of georeferencing themselves, such as a GNSS receiver. The positioning of all the mobile systems were based on the Simultaneous Localization and Mapping (SLAM) algorithm integrated with an inertial measurement unit (IMU), and they showed a similar precision; planar positioning error of less than 15 cm and vertical error of 10–30 cm. However, the accuracy of the only commercial system in this test whose positioning methods included a GNSS receiver, was order of several meters, indicating a demand for better methods for GNSS-based global positioning inside a dense forest canopy.