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1
IIMURA, Yutaka. "Toward the open-systematization of wooden civil engineering materials-Toward four million cubic meter of wood utilization in the civil engineering." Wood Preservation 38, no. 6 (2012): 244–50. http://dx.doi.org/10.5990/jwpa.38.244.
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Alder, Andy, Steve Hails, and Alex Vaughan. "Ensuring health, safety and well-being on the UK’s Thames Tideway tunnel programme." Proceedings of the Institution of Civil Engineers - Civil Engineering 175, no. 2 (May 1, 2022): 71–78. http://dx.doi.org/10.1680/jcien.21.00186.
Повний текст джерелаАнотація:
Due for completion in 2025, the £4.2 billion Thames Tideway tunnel programme is one of the largest and most complex civil engineering schemes in the world. This paper reports on how the delivery team ensured the health, safety and well-being of over 4000 people who worked on the programme during the first 6 years of its 9 year delivery. The team collaborated to create a strong safety culture, focusing on excellence in getting the basics right, sharing and adopting best practice, and learning from near misses and incidents. The result has been a very good level of safety performance.
3
Guillen Bonilla, Guillen Bonilla, Rodríguez Betancourtt, Casillas Zamora, Sánchez Morales, Gildo Ortiz, and Guillen Bonilla. "Signal Analysis, Signal Demodulation and Numerical Simulation of a Quasi-Distributed Optical Fiber Sensor Based on FDM/WDM Techniques and Fabry-Pérot Interferometers." Sensors 19, no. 8 (April 12, 2019): 1759. http://dx.doi.org/10.3390/s19081759.
Повний текст джерелаАнотація:
In civil engineering quasi-distributed optical fiber sensors are used for reinforced concrete monitoring, precast concrete monitoring, temperature monitoring, strain monitoring and temperature/strain monitoring. These quasi-distributed sensors necessarily apply some multiplexing technique. However, on many occasions, two or more multiplexing techniques are combined to increase the number of local sensors and then the cost of each sensing point is reduced. In this work, a signal analysis and a new signal demodulation algorithm are reported for a quasi-distributed optic fiber sensor system based on Frequency Division Multiplexing/Wavelength Division Multiplexing (FDM/WDM) and low-precision Fabry-Pérot interferometers. The mathematical analysis and the new algorithm optimize its design, its implementation, improve its functionality and reduce the cost per sensing point. The analysis was corroborated by simulating a quasi-distributed sensor in operation. Theoretical analysis and numerical simulation are in concordance. The optimization considers multiplexing techniques, signal demodulation, physical parameters, system noise, instrumentation, and detection technique. Based on our analysis and previous results reported, the optical sensing system can have more than 4000 local sensors and it has practical applications in civil engineering.
4
Abbas, Sameer Sh, Muhanna M. Ahmed, Ali M. Abed, and Firas H. Al-Menshed. "Application of 2D and 3D Electrical Resistivity Imaging Techniques for Site Investigation in Ramadi City, Western Iraq." IOP Conference Series: Earth and Environmental Science 1080, no. 1 (September 1, 2022): 012011. http://dx.doi.org/10.1088/1755-1315/1080/1/012011.
Повний текст джерелаАнотація:
Abstract Ramadi city, western Iraq, is considered an area with risks resulting from the presence of gypsum soil near the surface and the water table on shallow depth which facilitates the solubility of the soil and creates a weak area. So a dipole-dipole array with an n factor of 6 and a -spacing of 2 m was used. Ten 2D resistivity imaging traverses and 3D resistivity imaging station were done. The robust constrained inversion method is used to obtain 2D and 3D models. The results show that the topsoil layer extends to 2m depth with resistivity of 800 to 4000 Ωm. This is caused by high inhomogeneities in the deposits. The weakness zones and Depositional lenses appears after 2m depth and extent to 9m with resistivity value extend from 200 to 800 Ωm. Finally, it is concluded that four main reasons for civil engineering failure in Ramadi city. These reasons may be the inhomogeneity of the underground deposition material. In addition, the existence of weak areas and sedimentation lenses, and the change of water table.
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Nazmeeva, T. V. "Bearing capacity of compressed continuous and perforated thin-walled steel members of C-shaped cold-formed profiles." Magazine of Civil Engineering 40, no. 5 (August 2013): 44–51. http://dx.doi.org/10.5862/mce.40.5.
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6
Morgenthal, G., R. Sham, and A. Schwarz. "The 4000 tonne lift of Stonecutters Bridge steel back-spans, H.K." Proceedings of the Institution of Civil Engineers - Bridge Engineering 161, no. 4 (December 2008): 197–208. http://dx.doi.org/10.1680/bren.2008.161.4.197.
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Wang, Jiachen, Zhilong He, Dantong Li, and Weifeng Wu. "Numerical Simulation of Vortex-Induced Vibration of TTR and SCR." Journal of Marine Science and Engineering 10, no. 5 (May 22, 2022): 708. http://dx.doi.org/10.3390/jmse10050708.
Повний текст джерелаАнотація:
Top tensioned risers (TTRs) and steel catenary risers (SCRs) have been widely used in the field of marine engineering. They are commonly used to transport fluids from subsea wells to surface platforms. Under the action of ocean currents, these risers are often subjected to vortex-induced vibrations (VIVs), which might lead to serious fatigue damage. In this study, VIV around TTR and SCR were numerically simulated using the computational fluid dynamics software FLUENT when the Reynolds number was 4000. In the calculations, the full hexahedron grid and large eddy simulation were used to ensure calculation accuracy from the boundary conditions, as well as solution control. The shape, frequency, and amplitude of VIV produced by TTRs and SCRs at different times and depths were simulated.
8
Shoenberger, James E. "Construction of Stone Matrix Asphalt Section at Edwards Air Force Base." Transportation Research Record: Journal of the Transportation Research Board 1543, no. 1 (January 1996): 29–37. http://dx.doi.org/10.1177/0361198196154300104.
Повний текст джерелаАнотація:
In February 1993, the U.S. Air Force Civil Engineering Support Agency asked the U.S. Army Engineer Waterways Experiment Station to provide technical assistance for construction of a stone matrix asphalt (SMA) pavement demonstration project at Edwards Air Force Base (AFB). In August 1993, approximately 0.8 km (0.5 mi) of SMA pavement was placed on a road at Edwards AFB. The SMA mixture contained crushed stone, natural sand, fly ash, cellulose fiber, and an AR-4000 asphalt cement. The following summer, it was reported that excessive amounts of bleeding had occurred in all wheelpaths. An inspection in August 1994 confirmed this finding, and it was noted that the bleeding was worse near the intersections. The SMA mixture apparently contained too much asphalt cement. Several factors contributed to the bleeding: (a) the SMA mixture as designed contained too many fines, especially in passing the No. 4 sieve, compared with current guidance from the National Asphalt Paving Association and others; (b) the void content of the mixture may have been inadequate; and (c) samples obtained from the in-place pavement had a finer grading and higher asphalt content than specified. The bleeding has caused concern; however, no maintenance has been performed on the SMA pavement and no measurable rutting has occurred in the wheelpaths.
9
Cooper, R. W. "The River Danube: An Examination of Navigation on the River." Journal of Navigation 50, no. 1 (January 1997): 77–84. http://dx.doi.org/10.1017/s0373463300023602.
Повний текст джерелаАнотація:
One of the definitions of Navigation that gets little attention in this Institute is ‘communication by canals and rivers’ (Oxford English Dictionary), and which our French friends call La Navigation. I have always found this subject fascinating, and have previously navigated the Rivers Mekong, Irrawaddy, Hooghly, Indus, Shatt-al-Arab, Savannah and Rhône. During the middle of 1995 I travelled by barge from the North Sea to the Black Sea via the River Rhine, the Rhein—Main—Donau—Kanal (RMDK) and the River Danube, a distance of approximately 4000 km. This voyage has only recently become possible with the opening of the connecting RMDK at the end of 1992, but has been made little use of because of the civil war in the former Yugoslavia.
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Kurniawan, Cyrilus Winatama, and Mahen Mahendran. "Elastic lateral buckling of cantilever Litesteel Beams under transverse loading." International Journal of Steel Structures 11, no. 4 (December 2011): 395–407. http://dx.doi.org/10.1007/s13296-011-4001-z.
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Stauskis, Vytautas. "PULSE LENGTH DEPENDENCE ON THE DECAY OF THE INTEGRATED PULSE ENERGY/INTEGRUOTO IMPULSO ENERGIJOS SLOPIMO PRIKLAUSOMYBĖ NUO SKIRTINGŲ IMPULSO ILGIŲ." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 6, no. 3 (June 30, 2000): 206–12. http://dx.doi.org/10.3846/13921525.2000.10531588.
Повний текст джерелаАнотація:
The paper deals with the influence of the pulse length on the decay of the sound field energy. Six pulse lengths— 2000, 2500, 3000, 3500, 4000 and 4500 ms—were selected for investigations. Investigations show that a 2500 ms pulse is too short to correctly assess the background noise time interval. Such pulse length is not suitable for experiments. 3000 ms is the right length, while 3500 ms may be too long, resulting in errors of measurement results. When the pulse length increases to 4000 ms, the decay starting from 2000 ms is different from the pulse length 2500 ms and 3000 ms. Background noise starts from 2300 ms for these pulses, while for a 4000 ms pulse it starts from 3200 to 3300 ms. The length of 4500 ms is completely not suitable for investigations because the background noise zone starts very early, ie at 1800 ms, while for a short 2500 ms pulse it starts much later, after 2300 ms. While investigating energy decay, it is important to determine the maximum decay. At 63 Hz the sound field decay is almost uniform till— 18 dB. Later the decay character is different. The decay of the longest (4500 ms) and the shortest (2500 ms) pulse after— 18 dB is very steep and reaches—30 dB. However, the decay is influenced by the background noise. Thus the shortest and the longest pulses are not suitable for the lowest frequencies. The greatest energy decay is characteristic of the 3000 ms pulse. After 1700 ms energy decreases to—30 dB. Thus at this frequency one may measure the echoing time while approximating decay from 0 to—20 dB. As the frequency increases, the results change. At 100 Hz the energy decays by— 35–37 dB at pulse lengths of 2500 ms and 4000 ms. The greatest decay of— 42 dB is produced by the longest pulse 4500 ms though this arouses certain doubts. Then the echoing time may be measured from 0 to— 30 dB. At 125 octave frequency the smallest maximum decay of— 40 dB is observed with the shortest pulse (2500 ms), while the largest one— 50 dB is produced by the longest pulse (4500 ms). Thus standard echoing time may be measured for this frequency. In the frequency range of 250–2000 Hz, the maximum energy decay is sufficient and amounts to— 50–60 dB. At 4000 Hz the final part of decay is strongly dependent on the pulse length although, as the decay is about— 55 dB in all cases, the standard echoing time may be measured correctly. Pulse length is important only for the calculation of the low-frequency echoing time. At 63–100 Hz the best maximum decay is seen with the pulse 3000 ms long, while at 125 Hz and over the best pulse lengths are from 3000 to 4000 ms. When the hall contains audience and tapestries are on the walls, the energy decay is almost uniform at the pulse lengths of 2000 to 2800 ms. In this case a better decay is obtained with the longest pulse of 2800 ms.
12
Czeszejko-Sochacka, Katarzyna. "Some remarks on the issues of the consequences of war rape on the example of Bosnia and Herzegovina." Polityka i Społeczeństwo 20, no. 1 (2022): 35–46. http://dx.doi.org/10.15584/polispol.2022.1.3.
Повний текст джерелаАнотація:
The civil war in Bosnia and Herzegovina was one of the bloodiest armed conflicts after the end of the Second World War. Despite the passage of years, it is still a painful part of reality for a large group of the country's population. During the war, human rights were violated in the form of ethnic cleansing, murders, and so-called genocidal rapes. Women who were raped face social stigma to this day. According to conservative estimates, approx. 4000 children were born as a result of rapes. Today, the adult generation of "children of shame" experiences social ostracism in almost all spheres of life. Their situation is affected by the fact that they are not recognized as "victims of war" under the current regulations. This situation is slowly beginning to change, but it is a long-term process that requires intensified efforts not only in Bosnia and Herzegovina, but also in the international arena.
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Ashveenkumar, P., M. Preethi, and P. Prashanth. "Mechanical properties of geopolymer concrete with varying cement content using flyash and ground granulated blast furnace slag." International Journal of Engineering, Science and Technology 13, no. 4 (May 30, 2022): 57–64. http://dx.doi.org/10.4314/ijest.v13i4.7.
Повний текст джерелаАнотація:
In the recent past, the importance of geopolymer concrete as an eco-friendly product to replace portland cement concrete is continuously increasing over time. Yet less research effort has been invested in this area compared with some topical issues in civil engineering. Thus, the objective of this article is to analyse the mechanical properties of geopolymer concrete where the cement is replaced by fly ash and ground granulated blast-furnace slag (GGBS). Sodium silicate and sodium hydroxide 8 molarity solution was used. The compressive strength of a cube in an 8 molarity solution was measured for various mixtures (i.e. G50F50 where G and F stand for GGBS and flyash, respectively while the numerical value denotes the cement percentage) and the cement contents (i.e. 0, 10, 20, 30, 40%). The cube specimens are 100mmx100mmx100mm with the ambient curing at 35- 400C. In total, 9 cubes, 3 beams and 3 cylinders are cast at 7days, 14days and 28days while the compressive strengths of different mixes and cubes are calculated. For 28days, beams and cylinders are measured for flexural and tensile strength. The compressive strength at 7,14 and 28 days nearly doubled the target strength by using geopolymer concrete instead of normal concrete. Compressive strength is about 10% higher at 7 and 14days and 20% higher at 28days after replacing 40% of the cement. Flexural strength increased by 50% when 40% of the cement was replaced but split tensile strength only increased by 1%.
14
Ali, Saqib, Haresh Kumar, Samar Hussain Rizvi, Muhammad Saleem Raza, and Jawaid Kamal Ansari. "Effects of Steel Fibres on Fresh and Hardened Properties of Cement Concrete." Civil and Environmental Engineering Reports 30, no. 3 (September 1, 2020): 186–99. http://dx.doi.org/10.2478/ceer-2020-0039.
Повний текст джерелаАнотація:
Abstract Concrete possesses distinct features that make it widely acceptable for use across the globe; however, along with its obvious benefits, it has numerous drawbacks i.e., it is brittle in nature and its production causes an adverse impact on the environment. To counter such problems, researchers around the world have introduced sustainable measures. Fibre addition is foremost among these solutions in that it prevents crack propagation and increases the overall strength of concrete. In the present age, civil engineering structures have their own structural and durability requirements and so, modification in traditional concrete has become a necessity. This research is targeted at steel fibre reinforced concrete (SFRC), which is a superior quality concrete because of its enhanced strength. The steel fibres are obtained from binding wire that is used to tie the steel reinforcement. By referring to past research, steel fibres with an aspect ratio (length to diameter ratio) of 30 were considered favourable. The controlled, mixed design of the concrete was prepared with a targeted strength of 4000 psi and, while mixing the concrete ingredients, fibres were added to allow uniform dispersion. The fresh and hardened properties of workability, compressive, and tensile strength were tested and the results of fibres at 0%, 1%, 2% and 3% concrete mass were compared and analysed. The results indicated that highest compressive and tensile strength values were achieved with 3% fibre addition. However, with further addition, it was observed that concrete loses its workability. Therefore, it is suggested that 1% addition of steel fibres produces good strength with sufficient workability.
15
Li, Jiulin, Qingquan Li, Qingzhou Mao, and Hao Xu. "Digital-Twin-Based High-Precision Assembly of a Steel Bridge Tower." Buildings 13, no. 1 (January 16, 2023): 257. http://dx.doi.org/10.3390/buildings13010257.
Повний текст джерелаАнотація:
Steel structures that benefit from having lightweight, ductility, and seismic behaviors are capable of improving the overall performance of civil engineering in environmental protection, project quality, process management, and ease of construction, making the procedure more feasible for builders. The application of steel structure techniques has been widely used in bridges, tall buildings, and complex projects around the world. Increasing demand for planning and design has led to structural projects upgrading in structural complexity and geometrical irregularity. However, steel structure projects are still limited by the principal disadvantage of susceptibility to deformation. Therefore, the challenges of the assembly and manufacturing process for steel structures are important. In this paper, to achieve full-loop tracking and control of the assembly and manufacturing process, we propose an integrated approach to undertake the aforementioned challenges via digital twin technology, which combines three modules: (1) deformation detection, (2) pose estimation and optimization, and (3) deformation correction and pose control. This proposed methodology innovatively merges gravitational deformation analysis with geometrical error analysis. Furthermore, the validity of this method’s implementation is demonstrated by the New Shougang Bridge project. The results show that the assembly precision satisfies the standard of less than H/4000, nearing H/6000. Moreover, the elevation difference is less than 20 mm, which satisfies the control precision of the geometric pose. The new method that we propose in this paper provides new ideas for structural deformation control and high-precision assembly, as it realizes dynamic deformation sensing, real-time deviation analysis and manufacturing, and efficient optimization of the assembly process.
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Yukhimchuk, A. A., V. V. Angilopov, V. A. Apasov, Yu I. Vinogradov, A. N. Golubkov, Ye V. Gornostaev, S. K. Grishechkin, et al. "Gas Feeding System Supplying the U-400M Cyclotron Ion Source with Hydrogen Isotopes." Fusion Science and Technology 48, no. 1 (August 2005): 704–7. http://dx.doi.org/10.13182/fst05-a1021.
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Wang, Xiangying. "Field Test Investigation of the Pile Jacking Performance for Prefabricated Square Rigid-Drainage Piles in Saturated Silt Sandy Soils." Advances in Civil Engineering 2019 (December 13, 2019): 1–11. http://dx.doi.org/10.1155/2019/4587929.
Повний текст джерелаАнотація:
The rigid-drainage pile, designed to accelerate the dissipation of excess pore water pressure around the pile, is a new type of pile that combines the bearing capacity of ordinary rigid piles and the draining capacity of gravel piles. Field tests of these new piles were performed for the first time at a construction site in the new campus of Jiangyin No. 1 High School. Numerous parameters were observed for the test piles in many trials, including the excess pore water pressures, horizontal soil pressures, and displacements. At the measuring position at 0.6 m from the pile center, the rigid-drainage pile dissipates 70% of the peak excess pore water pressure in 1000 s, whereas the ordinary pile requires nearly 4000 s to dissipate the identical amplitude. The field test results clearly demonstrate that the rigid-drainage pile can reduce the amplitude of the peak pressure caused by piling in the liquefiable layer, quickly dissipate the excess pore water pressure, reduce the loss of effective stress in the soil surrounding the pile, and maintain the foundation stability.
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Celes, Josepha D., and Paul W. Mayne. "Remediation and Transformation of Kaolin by Plasma Magmavication." Transportation Research Record: Journal of the Transportation Research Board 1714, no. 1 (January 2000): 65–74. http://dx.doi.org/10.3141/1714-09.
Повний текст джерелаАнотація:
In situ plasma magmavication is a powerful and expedient technique for melting soil that subsequently cools to form a glassy igneous rock. A nontransferred arc plasma torch provides temperatures exceeding 4000°C that can be positioned within boreholes as a means of ground improvement or for environmental restoration of contaminated soils. The process is similar to in situ vitrification by embedded graphite electrodes, yet the nontransferred arc is a considerably more efficient process. The artificial rock can be left in place or, alternatively, may be exhumed and stored. The effectiveness of plasma remediation on uncontaminated and contaminated kaolin was investigated through a preliminary series of laboratory chamber tests with small dosages of chemical, biological, and nuclear surrogates. It is believed that the process pyrolizes organic contaminants, while locking the inorganic contaminants within the glass matrix. Measurements in compressive strength, stiffness, porosity, and mass density verified the transformation of soil to rock with improved material characteristics.
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Renilson, Martin, and Andrew Tuite. "An Investigation into the Self-righting of a Modern Racing Yacht in Waves." Journal of Ship Research 45, no. 03 (September 1, 2001): 241–47. http://dx.doi.org/10.5957/jsr.2001.45.3.241.
Повний текст джерелаАнотація:
Ocean sailing yachts can, and do, capsize from time to time, and so the safety of those who sail on them is linked directly to their ability to self-right once capsized. Current regulations used for racing yachts are based on statical concepts, which have been shown to be inappropriate (Renilson et al 2000). In order to gain an understanding of the dynamic factors involved, experiments were conducted on a 1/12.5 scale model of an ocean sailing yacht in waves in the towing tank at the Australian Maritime College. Two different experimental procedures were developed: Testing in a single breaking wave, and testing in steep irregular waves. Four variations of the limit of positive stability were tested, together with one condition which had a different roll radius of gyration, without water on board the model. In addition, two variations of the limit of positive stability were tested to represent the condition with 4000 kg of water on board. From the tests it was possible to conclude that, for the given yacht, if the limit of positive stability is decreased from 119 deg to 104.7 deg the yacht is much less likely to self-right under the action of waves, with or without 4000 kg of water on board.
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Ines, Isakovic. "CRM performances accented with the implementation of e-commerce technology." Istrazivanja i projektovanja za privredu 11, no. 3 (2013): 153–59. http://dx.doi.org/10.5937/jaes11-4008.
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Guo, Junhua, Yutao Ye, and Yafeng Ma. "Route Selection and Distribution Cost of Express Delivery: An Urban Metro Network Based Study." Promet - Traffic&Transportation 33, no. 2 (April 1, 2021): 283–96. http://dx.doi.org/10.7307/ptt.v33i2.3592.
Повний текст джерелаАнотація:
Route selection and distribution costs of express delivery based on the urban metro network, referred to as metro express delivery (MeD), is addressed in this study. Considering the characteristics of express delivery transportation and the complexity of the urban metro network, three distribution modes of different time periods are proposed and a strict integrated integer linear programming model is developed to minimize total distribution costs. To effectively solve the optimal problem, a standard genetic algorithm was improved and designed. Finally, the Ningbo subway network is used as an example to confirm the practicability and effectiveness of the model and algorithm. The results show that when the distribution number of express delivery packages is 1980, the three different MeD modes can reduce transportation costs by 40.5%, 62.0%, and 59.0%, respectively. The results of the case analysis will help guide express companies to collaborate with the urban metro network and choose the corresponding delivery mode according to the number of express deliveries required.
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Pang, Yong, Ling Li, Guangbo Cui, and Qi Yao. "Identification of River Sections for Domestic Water Supply along the Yangtze River in Jiangsu Province, China." Water Resources Management 20, no. 1 (February 2006): 61–75. http://dx.doi.org/10.1007/s11269-006-4006-0.
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Zhu, Deliang, Yue Li, Lingwei Zheng, Pengfei Fang, and Xinyu Xie. "Laboratory Model Study on the Pile-Forming Mechanisms and Bearing Deformation Characteristics of CFA Piles." Advances in Civil Engineering 2021 (December 10, 2021): 1–10. http://dx.doi.org/10.1155/2021/4827596.
Повний текст джерелаАнотація:
To study the pile-forming mechanism and bearing deformation characteristics of continuous flight auger (CFA) piles, a series of procedures, including helical drilling, pulling up/grouting, and inserting cage/pile forming, were simulated in clay-sand double-layer foundations by a homemade model drilling machine system in laboratory model tests. The effects of two different pile-forming methods on the load transfer and bearing characteristics of the piles were investigated by performing a model test comparison of CFA piles and bored piles. The experimental results show that there exist a soil improvement effect around the pile and a diameter expansion effect during the drilling process and grouting process for the CFA pile, which can effectively improve the lateral friction resistance of the pile. Compared with the bored pile, the pile diameter in the middle of the CFA pile increased by 19%, and the total lateral friction resistance of the CFA pile increased by 9.1% at a high load (1500 N). The comparative results of the model tests show that the bearing capacity of a single CFA pile increased by 50.0% and that the total settlement decreased by 40.5%. The results of the in situ test piles show that the load-settlement curves of the two pile types are similar under low-medium loads and that the lateral friction resistance of the CFA pile under high loads is better developed, which is relatively consistent with the model test results.
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J. Edmunds, L. Franco, Thushara Jayasinghe, Thusitha Ginigaddara, Paulo Vaz-Serra, and Priyan Mendis. "Bridge deck analysis of transversely post-tensioned concrete box girder bridges." Electronic Journal of Structural Engineering 23, no. 1 (January 23, 2023): 46–63. http://dx.doi.org/10.56748/ejse.234101.
Повний текст джерелаАнотація:
For rural bridges in Australia, a common design practice is pouring in-situ concrete on top of beams in order to tie all the beams together and distribute load. However, pouring concrete on-site creates more risk and contractors prefer to avoid it. Another method is using transverse post tensioning to tie beams. This article investigated the behaviour of transverse post-tensioning bars in providing load distribution between beams and ultimately comment on their effectiveness compared to in-situ poured decks. Currently, the industry has not completely investigated this matter in order to design post-tensioning accurately. Conservative estimates are currently used in industry today. Current practice is 50% of the design load on the beam where the load is applied in their design assumptions which is quite high. The team modelled concrete box girder bridges with transverse post-tensioning using grillage method. Several factors were investigated including bridge length and width, bridge skew and beam type. From the models, the team concluded that increasing the bridge span increases the load distribution, the load distribution difference is negligible for skew between 0 and 20 degrees and larger shear actions are observed with increased skew and width. It was determined that the worst-case total load on the beam where the load as applied was found to be 40.5%, 9.5% less than current practice. It is recommended that a similar investigation is conducted using a finite element method to gain a deeper understanding.
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Blanco Espezua, María del Pilar. "Retorno económico de los graduados universitarios de la región Puno." Semestre Económico 9, no. 1 (June 30, 2020): 6–26. http://dx.doi.org/10.26867/se.2020.v09i1.96.
Повний текст джерелаАнотація:
El objetivo es identificar los factores socio económicos que influyen en la probabilidad de alcanzar un retorno en la educación superior universitaria en la región Puno. La metodología se basa en la utilización de la ecuación de Mincer, siendo la variable dependiente, los niveles de ingresos salariales mensuales del graduado. La información se obtuvo de una encuesta aplicada a jóvenes cuyo período de graduación fue 2008-2014 en universidades públicas y privadas de la región y se agruparon a los graduados por áreas de conocimiento tales como: Ciencias empresariales y económicas; Ciencias de vida humana; Ciencias sociales; Ingenierías de Construcción- Minería- Electricidad; Ciencias de la vida animal y Ciencias básicas. Inicialmente se realizó una descripción estadística de los datos y luego se aplicó la técnica de estimación econométrica de máxima verosimilitud, con el modelo probit ordenado y se analizaron los efectos marginales que explicaron que la probabilidad de obtener salarios mensuales altos depende de la carrera elegida, del sexo del graduado y de su edad, más no de su experiencia ni del nivel de educación alcanzado por los padres. Los resultados indican que, para ingresos entre 1001 y 2000 soles, destacan las carreras de Ciencias sociales. Para ingresos entre 2001 a 3000 soles, destacan las carreras de ciencias empresariales y económicas junto con las carreras de ciencias agrarias y ciencias de la vida animal. Finalmente, para ingresos entre 3001 a 4000 soles, destacaron las carreras de ingeniería, vinculadas a la construcción civil; minería y electricidad. Así como las carreras de ciencias de la vida humana, destacando medicina.
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Al-Manaseer, A. A., and K. W. Nasser. "Laboratory and field tests with a new nondestructive apparatus." Canadian Journal of Civil Engineering 17, no. 6 (December 1, 1990): 904–10. http://dx.doi.org/10.1139/l90-102.
Повний текст джерелаАнотація:
A new nondestructive test for estimating the compressive strength of concrete and mortar at early ages is described in this paper. The pin penetration test was used to relate the early age strength of hardened concrete and mortar in the laboratory. It was found that the pin penetration tester can be used successfully, under laboratory conditions, to determine the compressive strength of concrete cylinders and mortar slabs at early age from 10 hours up to 28 days. For concrete and mortar cylinders, slabs, and cubes with a compressive strength of up to 27.6 MPa (4000 psi), the pin penetration readings were found to be linearly related to the compressive strength. The tester was also used successfully in the field to determine the compressive strength of a concrete floor slab in a new building in order to post-tension the strands and remove the forms. The building was constructed in winter under severe climatic conditions. Key words: early age, strength evaluation, concrete slabs, form removal, nondestructive tests, mortar testing, pin penetration test.
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Hynes, Thomas P., Tim Meadley, and Neill Thompson. "Effluent treatment experience at a high-grade uranium mine." Canadian Journal of Civil Engineering 13, no. 4 (August 1, 1986): 429–37. http://dx.doi.org/10.1139/l86-067.
Повний текст джерелаАнотація:
Amok Ltd. is the operator of uranium mining and milling facilities at Cluff Lake in northwestern Saskatchewan. All contaminated liquid effluents from these facilities have been subject to treatment by chemical and physical methods before release to the environment. In particular, a secondary treatment system (STS) has been operated adjacent to the tailings management area to reduce the concentration of radium-226 to below the maximum levels allowable in the final effluent. The STS has operated for over 2 years at a nominal rate of 4000 m3/day. During this time, the most stringent regulatory limit on radium-226 concentration (0.37 Bq/L = 10 ×10−12 g/L total, based on a monthly arithmetic mean) has been exceeded on only two occasions. The process regularly removes 99% of the radium from the effluent stream. Data is presented on chemical addition rates, efficiencies of system components, and the significance of each stage of the treatment process. In addition, several modifications have been made to the STS. Recently, a primary treatment system has been added to the effluent treatment process. Preliminary indications are that this system has increased the overall efficiency of the system.
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Chin, Cheng Siong, Yan-Jie Tan, and Mohan Venkatesh Kumar. "Study of Hybrid Propulsion Systems for Lower Emissions and Fuel Saving on Merchant Ship during Voyage." Journal of Marine Science and Engineering 10, no. 3 (March 9, 2022): 393. http://dx.doi.org/10.3390/jmse10030393.
Повний текст джерелаАнотація:
The hybrid propulsion system is a vehicle propulsion system with two or more sources of propulsion such as diesel, batteries, and other renewable energy. The use of hybrid propulsion systems is not new, and they have been adopted worldwide. There are many applications for hybrid propulsion systems, from powering land-based vehicles to marine vessels. With the success of hybrid propulsion systems, many large vessels still rely on two-stroke engines for power generation. In this paper, the benefits and feasibility of using battery systems or hybridizing existing conventional two-stroke engines onboard large intercontinental vessels is studied and simulated. The merchant ship, a bulk carrier with 82,000 deadweight tonnage capacity, is used. The model vessel travels along a simulated route of up to 4000 nautical miles using weather routing software to generate data for estimating emissions with the help of widely adopted empirical formulas. A reduction of up to 3.4 tonnes of emissions and fuel consumption of not more than 1 tonne per kWh from peak shaving and boosting applications for a 12-day voyage were observed.
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Nouri, Ali, and Sohrab Astaraki. "Optimization of Sound Transmission Loss through a Thin Functionally Graded Material Cylindrical Shell." Shock and Vibration 2014 (2014): 1–10. http://dx.doi.org/10.1155/2014/814682.
Повний текст джерелаАнотація:
The maximizing of sound transmission loss (TL) across a functionally graded material (FGM) cylindrical shell has been conducted using a genetic algorithm (GA). To prevent the softening effect from occurring due to optimization, the objective function is modified based on the first resonant frequency. Optimization is performed over the frequency range 1000–4000 Hz, where the ear is the most sensitive. The weighting constants are chosen here to correspond to an A-weighting scale. Since the weight of the shell structure is an important concern in most applications, the weight of the optimized structure is constrained. Several traditional materials are used and the result shows that optimized shells with aluminum-nickel and aluminum-steel FGM are the most effective at maximizing TL at both stiffness and mass control region, while they have minimum weight.
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Mazari, Adnan, and Antonin Havelka. "Impact of stitch length on sewing needle temperature." World Journal of Engineering 11, no. 2 (June 1, 2014): 187–92. http://dx.doi.org/10.1260/1708-5284.11.2.187.
Повний текст джерелаАнотація:
In this article the sewing needle heat is measured without sewing thread and with sewing thread at different stitch density (stitches per inch or SPI) of lock stitch sewing machine by thermocouples. Two methods are used to measure sewing needle heat, touch thermocouple method and inserted thermo couple method. Needle temperature is measured after periodic 10, 20, 30 and 60 seconds of sewing operation. Whereas the machine running at speed from 1000 r/m to 4700 r/m. It is observed that decreasing stitch length causes an increase in the temperature of the sewing needle. Stitch density shows same influence on needle for sewing with thread and without thread. It is observed from our research that at SPI of 14 the needle temperature with thread rises to 259 °C at 4000 r/min of machine. It is recommended to use minimum stitch density.
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Kirik, Ekaterina, Aleksey Bogdanov, Olga Sushkova, Marina Gravit, Daria Shabunina, Artem Rozov, Tatyana Vitova, and Yuriy Lazarev. "Fire Safety in Museums: Simulation of Fire Scenarios for Development of Control Evacuation Schemes from the Winter Palace of the Hermitage." Buildings 12, no. 10 (September 27, 2022): 1546. http://dx.doi.org/10.3390/buildings12101546.
Повний текст джерелаАнотація:
The manuscript is focused on the problems of evacuation in case of fire from the buildings of museums as places with a mass presence of people. Features specific to museums and how they affect safe evacuation conditions are discussed. Most attention is paid to evacuation management, since the vast majority of museum visitors are not familiar with the layout of the building. In this case, the actions of staff in evacuation management are decisive. The paper considers the development of evacuation schemes, taking into account the spread of fire hazards in the building and the development of instructions on their basis for the staff. Using the example of the Winter Palace of the State Hermitage Museum, the solution of the marked tasks with the use of computer simulation of evacuation during a fire is given. The analysis of the simulation results showed the vulnerabilities of the museum. In this work, the evacuation schemes for the scenarios are considered. The maximum number of visitors at a single time in the Winter Palace has been set at 4000. The principles of making evacuation schemes are formulated, including taking into account the peculiarities of space-planning solutions inherent in museums, such as enfilades and the connections of rooms.
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Xi, Xun, Shangtong Yang, Christopher I. McDermott, Zoe K. Shipton, Andrew Fraser-Harris, and Katriona Edlmann. "Modelling Rock Fracture Induced By Hydraulic Pulses." Rock Mechanics and Rock Engineering 54, no. 8 (April 30, 2021): 3977–94. http://dx.doi.org/10.1007/s00603-021-02477-0.
Повний текст джерелаАнотація:
AbstractSoft cyclic hydraulic fracturing has become an effective technology used in subsurface energy extraction which utilises cyclic hydraulic flow pressure to fracture rock. This new technique induces fatigue of rock to reduce the breakdown pressure and potentially the associated risk of seismicity. To control the fracturing process and achieve desirable fracture networks for enhanced permeability, the rock response under cyclic hydraulic stimulation needs to be understood. However, the mechanism for cyclic stimulation-induced fatigue of rock is rather unclear and to date there is no implementation of fatigue degradation in modelling the rock response under hydraulic cyclic loading. This makes accurate prediction of rock fracture under cyclic hydraulic pressure impossible. This paper develops a numerical method to model rock fracture induced by hydraulic pulses with consideration of rock fatigue. The fatigue degradation is based on S–N curves (S for cyclic stress and N for cycles to failure) and implemented into the constitutive relationship for fracture of rock using in-house FORTRAN scripts and ABAQUS solver. The cohesive crack model is used to simulate discrete crack propagation in the rock which is coupled with hydraulic flow and pore pressure capability. The developed numerical model is validated via experimental results of pulsating hydraulic fracturing of the rock. The effects of flow rate and frequency of cyclic injection on borehole pressure development are investigated. A new loading strategy for pulsating hydraulic fracturing is proposed. It has been found that hydraulic pulses can reduce the breakdown pressure of rock by 10–18% upon 10–4000 cycles. Using the new loading strategy, a slow and steady rock fracture process is obtained while the failure pressure is reduced.
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Sobotova, Lydia, and Miroslav Badida. "Laser marking as environment technology." Open Engineering 7, no. 1 (November 23, 2017): 303–16. http://dx.doi.org/10.1515/eng-2017-0030.
Повний текст джерелаАнотація:
AbstractThe contribution deals with the laser marking as one of the progressive and environment friendly technologies with utilisation in many branches of industry. Engraving and other types of laser marking of different types of materials are very actual technologies these days. Laser marking decreases the waste creation in comparison with the other classical marking technologies, which use paintings or created chips. In this experimental investigation the laser marking surface texturing of material AL99,7 according to STN 42 4003:1993-08 (STN EN 573) has been conducted. The laser marking machine TruMark 6020 and software TruTops Mark were used. Laser surface texturing after laser marking has been realised under different combinations of process parameters: pulse frequency, pulse energy and laser beam scanning speed. The morphological characterization of engraving or annealing surfaces has been performed using scanning electron microscopy (SEM) technique. The evaluation of roughness of engraved surfaces has been realized according to STN EN ISO 4287 by using Surftest SJ 301. The aim of the contribution was to show how different laser parameters affect the surface texture and colour change of metallic materials while creating minimal waste.
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Lebedevas, Sergejus, Justas Žaglinskis, and Martynas Drazdauskas. "Development and Validation of Heat Release Characteristics Identification Method of Diesel Engine under Operating Conditions." Journal of Marine Science and Engineering 11, no. 1 (January 11, 2023): 182. http://dx.doi.org/10.3390/jmse11010182.
Повний текст джерелаАнотація:
The decarbonisation of maritime transport in connection with the European Union and International Maritime Organisation directives is mainly associated with renewable and low-carbon fuel use. For optimisation of energy indicators of ship power plants in operation on renewable and low-carbon fuel, it is rational to use numerical research methods. The purpose of this research is to devise methodological solutions for determining the heat release characteristics, m and φz parameters of Wiebe model that can be applied to mathematical models of diesel engines under operating conditions. Innovative solutions are proposed, which in contrast with the methods used in practice, are not related to experimental registration of combustion cycle parameters. These registration techniques were replaced by the proposed exhaust gas temperature or exhaust manifold surface temperature registration method. The acceptable accuracy of results validates the methodological solutions for solving practical tasks: according to the Wiebe model, the error of determining m and φz compared with experimental data does not exceed 3–4%. The proposed method was implemented by simulating the energy indicators of two diesel engines, car engine 1Z 1.9 TDI (Pe = 66 kW; n = 4000 RPM) and multipurpose 8V396TC4 (Pe = 380–600 kW; n = 1850 RPM), in a single-zone model. The variation in experimental data when the engines operated on both diesel and rapeseed methyl ester (a biodiesel fuel), was approximately 1%. The authors anticipate further development of completed solutions with their direct application to ship power plants in real operating conditions.
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Yan, Shanlin, Jinwu Wu, Jie Chen, Qibo Mao, and Xiang Zhang. "Design of Honeycomb Microperforated Structure with Adjustable Sound Absorption Performance." Shock and Vibration 2021 (June 21, 2021): 1–12. http://dx.doi.org/10.1155/2021/6613701.
Повний текст джерелаАнотація:
In this work, a double-layer honeycomb microperforated structure with adjustable back-cavity’s height is designed based on cylinder honeycomb structure and microperforated panel (MPP). The sound absorption performance can be changed by adjusting the height of back-cavity. Thus, a better absorption performance is achieved by changing the position of the inner MPP. Acoustic impedance of the structure was calculated based on transfer matrix method. The sound absorption coefficient of the structure was obtained by finite element method (FEM). Meanwhile, the 3D printing technology was used to produce the experimental samples. The experimental results demonstrate that the sound absorption coefficient of the structure is greater than 0.8 in the range of 750–1250 Hz, greater than 0.9 in the range of 2297–3592 Hz, and above 0.5 in the range of 500–4000 Hz. In addition, the feasibility of achieving adjustable sound absorption by means of changing the height of the back-cavity is verified by theoretical, simulation, and experimental results. The structure proposed in this work can realize the function of wide-band and better sound absorption performance by changing the position of the inner MPP, which can be applied to effectively reduce different frequencies noise.
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SöRensson, Anna, and Lage Burström. "Energy Absorption of Vibration in the Hand for Higher Frequencies." Journal of Low Frequency Noise, Vibration and Active Control 15, no. 2 (June 1996): 71–79. http://dx.doi.org/10.1177/026309239601500202.
Повний текст джерелаАнотація:
The aim of this study has been to develop a measurement method to study the absorption of vibration energy on exposure to high frequency vibrations. The developed measurement method consists of specially constructed equipment for measurement and analysis of the subject's absorption of vibration energy. In this study the energy absorption from the exposure to white noise vibration within the frequency-range 20 to 5000 Hz has been studied. Five female and five male subjects were involved in this study. The results show that the developed method of measurement works satisfactorily and gives reliable results for the energy absorption within the frequency-range 20 to 4000 Hz. Furthermore, the results show that the subjects absorb vibration energy even for frequencies above 1000 Hz. The results also show that the energy absorption is dependent upon factors such as gender, the level of the vibration and the frequency.
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Scacco, Umberto, Francesco Tiralongo, and Emanuele Mancini. "Feeding in Deep Waters: Temporal and Size-Related Plasticity in the Diet of the Slope Predator Fish Coelorinchus caelorhincus (Risso, 1810) in the Central Tyrrhenian Sea." Journal of Marine Science and Engineering 10, no. 9 (September 2, 2022): 1235. http://dx.doi.org/10.3390/jmse10091235.
Повний текст джерелаАнотація:
In-depth studies on the effect of size and period in the diet of the hollow-snout grenadier Coelorinchus caelorhincus in the Mediterranean Sea are scant and incomplete. We obtained 75 specimens of this species from the discard of deep trawl fishing on the slope of the central Tyrrhenian Sea. As corollary data, we estimated the length–weight relationship, the size frequency distribution, and composition of sexual maturity stages of the sampled individuals. We deepened stomach content analysis aiming at the evaluation of size and period’s effect in the fish diet by Costello’s interpretation of dietary indexes and correspondence analysis. The corollary results suggested negative allometric growth (b = 2.69), an asynchronous reproductive strategy (paucity of mature individuals) and a size-related bathymetrical distribution for this species (prevalence of small and intermediate-sized specimens). The prey importance index (PII) revealed that the hollow-snout grenadier is a generalist feeder on cephalopods (PII: 0–1200), fish (PII: 0–1000), crustaceans (PII: 4000–6000), and polychaetes (PII: 400–1800), and a light specialist at population level on the dominant prey among them. At the micro-taxa level, the species was found to be a generalist feeder on 10 groups of rare prey and a light specialist at population level on amphipods (PII: 1300–3200). Overall, results indicated the presence of two feeding gradients that determined an intermingled effect of size and period on fish diet. In particular, intraspecific competition and stability of food resources appeared as the factors that significantly harmonize the diet of Coelorinchus caoelorhincus in the context of the ecotrophic constraints of a deep-sea species.
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Tao, ZhiGang, HuiXia Xu, Chun Zhu, Qian Lv, and Yong Wang. "The Study of the Supernormal Mechanical Properties of Giant NPR Anchor Cables." Shock and Vibration 2020 (March 16, 2020): 1–13. http://dx.doi.org/10.1155/2020/2621909.
Повний текст джерелаАнотація:
Due to the frequent occurrence of geological disasters, such as geological faults, tectonic activities, and local activities, the study of a cable structure capable of resisting large deformations and of absorbing energy is investigated. The plane length is increased step by step based on the deformation and energy absorption values of the original NPR anchor cable model. Three kinds of two-stage constant resistance bodies are designed following the three principles: first-stage friction plus second-stage expansion, primary expansion plus secondary expansion, and first-stage expansion plus second-stage friction. Moreover, a giant NPR anchor cable with extraordinary mechanical properties is developed. Via a theoretical analysis and laboratory static tensile tests on traditional NPR and giant NPR anchor cables, their force characteristics, constant resistance, and fluctuation trends are related to the size and the structure of the constant resistance body. In addition, the most remarkable improvement takes place in the cables’ deformation and energy absorption properties. The deformation increases from 1000–2000 mm to 3000–4000 mm, while the energy absorption value increases from 4.21 × 105–1.09 × 106 J to 3.2 × 106 J. The constant resistance value is also effectively enhanced to 550–723.7 kN. This provides a reliable technical support for their application in deep geological faults.
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Khidmat, Rendy Perdana, Hiroatsu Fukuda, and Kustiani. "Design Optimization of Hyperboloid Wooden House Concerning Structural, Cost, and Daylight Performance." Buildings 12, no. 2 (January 23, 2022): 110. http://dx.doi.org/10.3390/buildings12020110.
Повний текст джерелаАнотація:
The use of parametric and multi-objective optimization (MOO) as a new way of approaching architectural design has been growing in line with current breakthroughs in computational architecture. Wood, on the other hand, is a living and unique building material that provides durability, manufacturing flexibility, and local availability. One of the structure types that provides high structural stability is the hyperboloid. However, the exploration of hyperboloid structures in building design, together with the building daylight objective, is still limitedly reported. This paper presents the application of the parametric approach and multi-objective optimization in optimizing the structure and daylight objectives of a hyperboloid two-story wooden house in Japan, made of 105 mm × 105 mm × 4000 mm Japanese timber. The method involves iterating dynamic parameters such as radius bottom, offset distance, timber members, twisting level, building height, radius-top, and roof slope to optimize the structural objective of minimizing normal force average, displacement, and cost while simultaneously maximizing building volume. Regarding daylight objectives, unit movement and glazing ratio that control the glazing strategies were explored to optimize useful daylight illumination (UDI) in summer and winter. The optimization and exploration yielded 10,098 solutions in structural analysis and 406 solutions in daylight exploration. Based on the data analysis, the proposed methodology has successfully produced the best design solution, discovering the balance between the objective trade-offs. In addition, the most influential parameter that shapes the value of design objectives has been identified. The findings of this research were expected to contribute to and enhance the performance-based design optimization, and support design decision-making process in the early design stage of a wooden house with a hyperboloid structure.
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Karbauskaitė, Jūratė, and Vytautas Stankevičius. "HEAT DEMAND FOR HEATING APARTMENT BUILDINGS/GYVENAMŲJŲ NAMŲ FAKTINIO ŠILUMINĖS ENERGIJOS POREIKIO SULYGINIMAS SU PROJEKTINE ŠILDYMO SISTEMŲ GALIA." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 6, no. 5 (October 31, 2000): 366–70. http://dx.doi.org/10.3846/13921525.2000.10531615.
Повний текст джерелаАнотація:
In this paper the results of statistic analysis of heat consumption in apartment heating systems for Lithuania are discussed. Kaunas district heating system data are used for the analysis. Total sum of buildings involved is about 1900, including 1550 with the average heated area of 4000 m2. It has been established that real heat consumption in apartment buildings is less than the design heat demand (Fig 1), especially in small buildings (Fig 2). The distribution of monthly differences is presented in Fig 3. The difference during months does not depend on average outdoor temperature, but it could be caused by temperature fluctuations and solar radiation. It is quite important to determine the reasons of different heat consumption in buildings. For this purpose 20 dwelling houses of various design and building period, with various energy consumption problems have been selected for more detailed energy audit. Volumes of external building elements, changes in destination of premises, heated area have been estimated as well as the state of heat supply sub-station equipment. According to the data obtained, the energy consumption was determined for standard month at mean indoor and outdoor climate values. The results are compared with real energy consumption in the selected buildings and design values. It has been established that the inadequacies in exceeded energy consumption over design values are mostly caused by incorrect heated area registration and premises destination change, in a less range by absence of maintenance, eg broken outside doors, damaged roofs etc. Energy consumption in dwelling houses with design indoor temperature and normal maintenance level usually is near to the design value or less up to 10%. In dwelling houses, in which energy consumption is defined as being of less design value, some energy saving measures are applied, eg temperature in spaces is lowered up to 16°C, about half of balconies are glassed, electric stoves for cooking are installed as additional heat source. Such apartment buildings, as a rule, do not have premises of other destination. By such means near 40% of heat is saved.
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Asril, Muhammad, Salsabila Sugiarto, and Alfian Zurfi. "Airborne Microbial Quality Assessment in the Educational Buildings during the COVID-19 Pandemic." Civil Engineering Journal 9, no. 1 (January 1, 2023): 114–26. http://dx.doi.org/10.28991/cej-2023-09-01-09.
Повний текст джерелаАнотація:
Rooms with pollutants have a poor impact of 2-5 times greater than outdoors. The lecture hall had the potential to experience a decrease in air quality. This study was conducted to assess microbiological air quality in the general lecture building I Institut Teknologi Sumatra, Lampung, Indonesia, during the COVID-19 pandemic and its relationship with environmental conditions. This study was conducted using a settling sampling technique to count the number of bacteria and fungi in the air. Samples were collected twice daily for five working days. The results showed that the highest concentrations of bacteria and fungi were found at the wifi corner location, at 36.7–1237.2 CFU/m3 and 225.4–1431.2 CFU/m3, respectively. The highest average concentrations of bacteria and fungi at the wifi corner location were found in the afternoon at 479.1 ± 438.1 CFU/m3 and 800 ± 548.4 CFU/m3, respectively. The three locations did not meet the standards of room suitability for humans with immunodeficiencies based on the ACGIH. The location of the wifi corner did not meet the standards of the Minister of Manpower of the Republic of Indonesia No. 5 of 2018 and the WHO regarding microbial standards in the room. The highest value of the Global Microbial Contamination Index (GIMC/m3) was found in the wifi corner (G4: ≥2000 – ≤4000), which is closely related to population density and ventilation. Environmental factors influence the density of bacteria and fungi at the sampling sites. The relative humidity strongly influenced the concentration of fungi. In addition to relative humidity, bacterial density is also affected by light intensity and the number of people. This indicates that despite restrictions on activities during the COVID-19 pandemic, the room at GKU 1 did not meet the eligibility requirements for students with immune disorders. Doi: 10.28991/CEJ-2023-09-01-09 Full Text: PDF
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Stauskis, Vytautas. "THE FEATURES OF CINEMA HALL ACOUSTICS UPON INSTALLATION OF THE DOLBY SOUND RECORDING SYSTEM/KINO TEATRO AKUSTIKOS YPATUMAI, ĮRENGUS “DOLBY” ĮGARSINIMO SISTEMĄ." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 5, no. 5 (October 31, 1999): 312–17. http://dx.doi.org/10.3846/13921525.1999.10531481.
Повний текст джерелаАнотація:
Investigations conducted in a cinema hall have shown that the character of the sound field decay in all rows of the main floor is uniform. The character of the sound field decay in the balcony is similar to that on the main floor. The maximal decay energy in the balcony is lower by about 2 dB compared to that on the main floor. After the reconstruction of the hall, the energy decay of a similar character was found both on the main floor and in the balcony. The decay of energy is much faster because the sound absorption of the entire hall has increased. The maximal energy values, however, are higher in the balcony and under it compared to the main floor. After the reconstruction the overall hall absorption has increased by about 200–300 m2 both on the main floor and in the balcony. Consequently, the reconstruction should have resulted in the decrease of the maximal energy in both areas. Actually, the maximal energy value is higher in the balcony. At the frequency 63 Hz, the maximal energy value in the balcony after the reconstruction, ie after the increase in the overall absorption, is by 10 dB higher than that before reconstruction when the absorption was smaller. One would expect a reverse. A similar effect is observed in the rows under the balcony. At 1000 Hz and 2000 Hz the energy increase is 4–5 dB and it starts after 50 ms. At 4000 Hz a maximal energy increase of 7–8 dB is reached after 100 ms. Before the reconstruction the early reverberation time T10 markedly exceeded the permissible upper limit in all rows of the hall, and particularly at the end of the hall and in the balcony at the frequency from 63 to 500 Hz. As the sound field decay was approximated by larger level intervals, eg from 0 to −30 dB, still larger reverberation time values were obtained. After the reconstruction the early reverberation time in all rows of the main hall and the balcony does not exceed the permissible upper limit. It is only in the frequency range of 250–1000 Hz that the reverberation time values are below the lower limit. In this case, the listener's subjective perception will be of a weaker sound, which is strongly preferable, since the sound is too strong in Lithuanian cinema halls where the Dolby sound-recording system has been installed.
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Kolhe, Kishor Purushottmrao. "Testing of tractor mounted and self propelled coconut climber for coconut harvesting." World Journal of Engineering 12, no. 4 (August 1, 2015): 399–406. http://dx.doi.org/10.1260/1708-5284.12.4.399.
Повний текст джерелаАнотація:
The coconut is known as Kalpa Vriksa to the world for being its multi faceted uses, which provide livelihood security to millions of people. Every part of it useful to humans in one of the other ways. The coconut palm is grown in more than 93 countries of the tropics. Its botanical name is Cocos-Nucifera L. and belongs to the aracaceae (Palm) family. The climbing methods of coconuts like manual, mechanical and climbing by Tractor Operated Hydraulic Elevator (TOME) were studied. The stability, safety, harvesting efficiency, drudgery of coconut harvesting is reduced by Tractor Mounted and Self Propelled Coconut Climber (TMSPCC) developed by considering the drawbacks of the above methods. The testing of developed TMSPCC was carried out at a Coconut Research Station, Bhyte Ratnagiri, India. To assess the physiological cost and the drudgery involved in the traditional method of tree climbing operation. The digital polar hart rate meter RS400TM having infrared connectivity sensor was used for recording the heart rates. The technical assessments included the use of biomechanical models, ODR, BPDS. The ergonomical evaluation of TMSPCC was carried out for testing feasibility, ease of operation; workers jeopardize safety health and efficiency for coconut harvesting. Ergonomically operational safe and controlled heart rates are recorded. The fourteen to seventeen number of coconut orchards were harvested in one hour by using TMSPCC. The tractor mounted and self propelled coconut climber founds suitable for harvesting 100 to 120 coconut trees in a day. The net coconut harvesting by using TMSPCC are 4000 coconuts/day. Also TMSPCC is safe, less hazardous and economical as compared to manual climbing coconut harvesting and climbing by the existing tractor mounted hydraulic elevator.
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Wang, Haibo, Ming Cai, Shuqi Zhong, and Feng Li. "Sound field study of a building near a roadway via the boundary element method." Journal of Low Frequency Noise, Vibration and Active Control 37, no. 3 (August 21, 2017): 519–33. http://dx.doi.org/10.1177/1461348417725955.
Повний текст джерелаАнотація:
A two-dimensional boundary element method with a constant element type was adopted to study the sound field of a building near a roadway. First, a factor analysis of the computed results has been done, which include the element length, the Hankel functions’ calculation accuracy, and numerical integration accuracy. Then, boundary element method is applied to calculate building attenuation with different building aspect ratios and different frequencies with balconies, followed by drawing of the sound field distribution diagram. The calculation results revealed the following: (1) a wider building results in a more severe sound attenuation; (2) balconies on different floors produce a reduction of approximately 15 dB for broadband spectral characteristics of A-weight road traffic noise, and the maximum values appear at the bottoms of balconies; (3) for the points in the balconies, higher sound frequencies are correlated to larger insertion loss, with the insertion loss increasing from 3 dB to >10 dB when the sound frequency increases from 20 to 4000 Hz; (4) calculations of three typical frequencies indicate that the insertion loss of 500 Hz (main frequency of heavy vehicles) is 6 dB less than that of 800 Hz (main frequency of light vehicles), i.e. the flow control of heavy vehicles could conspicuously improve the ambient acoustic environment of buildings near a roadway.
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Ziayi Ghahnavieh, Niloofar, Siamak Pourabdian, and Farhad Forouharmajd. "Protective earphones and human hearing system response to the received sound frequency signals." Journal of Low Frequency Noise, Vibration and Active Control 37, no. 4 (April 8, 2018): 1030–36. http://dx.doi.org/10.1177/1461348418765958.
Повний текст джерелаАнотація:
Sound is one of the most important problems in industrial environments, and it causes hearing loss at different frequencies in the workforce. Incorrect fitting of hearing protector has a negative effect on noise reduction. The present study was conducted with the aim of determination of the effective frequencies on hearing loss and variations of the sound level in different frequencies after placing the earplug. A model of ear canal with different materials was simulated. Sound pressure sensors and earplugs were placed in both sides of the ear canal. The rates of sound reduction in octave frequency signals were calculated for the simulated canal of different materials, in different distances between the microphone and the earplug with Labview software. The results of sound simulation in octave frequency signals showed that by increasing the frequency, the rates of sound reduction in different conditions also had an increasing trend. The obtained peak rates for all the situations coincided with each other at fixed frequencies. In most cases, a noise reduction in the frequency of 4000 Hz showed a high number. The maximum sound reduction was observed at 25.5 mm at frequencies below 250 Hz, which was similar to the average of human ear canal length; so the simulated model can be used to determine the performance of the protective earphones and test them at different frequencies and sound pressure levels.
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Majdi, Hasan Shakir, Mahmoud A. Mashkour, Laith Jaafer Habeeb, and Marko Ilic. "Mixed convection around a circular cylinder in a buoyancy-assisting flow." Curved and Layered Structures 9, no. 1 (January 1, 2022): 81–95. http://dx.doi.org/10.1515/cls-2022-0008.
Повний текст джерелаАнотація:
Abstract In this paper, the effect of mixed convection on the flow behavior and heat transfer around a circular cylinder disclosed to a vertically upward laminar air stream is numerically examine. The buoyancy-aided flow is utilized to eliminate and control the vortex shedding of the cylinder. The influence of the Grashof number, 0 ≤ Gr ≤ 6000, the flow and thermal patterns, as well as the local and mean Nusselt number, is investigated at a constant Reynolds number of 100. The unsteady Navier-Stokes’s equations are solved employing a finite-volume method to simulate numerically the velocity and temperature fields in time and space. The results showed periodic instability in the flow and thermal fields for a range of Grashof number Gr ≤ 1300. Also, there is critical value of Grashof number for stopping this instability and the vortex shedding formed behind the cylinder, by the effect of heating. Thus, by increasing Grashof number between 1400 ≤ Gr ≤ 4000, the periodic flow vanishes and converts into steady flow with twin eddies attached to the cylinder from the back. Furthermore, as Grashof number increases behind Gr ≥ 5000, the flow becomes completely attached to the cylinder surface without any separation.
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Назимов, Андрей Ливерьевич, and Дмитрий Иванович Варыбок. "Mutual influence of local resistance and turbulent fluid flow in main pipelines." SCIENCE & TECHNOLOGIES OIL AND OIL PRODUCTS PIPELINE TRANSPORTATION, no. 4 (August 31, 2022): 340–51. http://dx.doi.org/10.28999/2541-9595-2022-12-4-340-351.
Повний текст джерелаАнотація:
В процессе эксплуатации иногда даже небольшие пульсации давления могут стать причиной значительных механических колебаний (вибраций) трубопровода и связанного с ним оборудования. Очевидно, что если частота поперечных колебаний трубы вследствие вибрации оборудования равна частоте собственных колебаний участка трубопровода, то возникнут резонансные колебания, амплитуда которых в десятки раз превысит амплитуду возбуждающих колебаний. Вибрационные нагружения в результате случайных или периодически повторяющихся переходных процессов приводят к сокращению безопасного срока эксплуатации конструкций с дефектами, образованию трещин в сварных швах. Детерминированная оценка прочности и ресурса долговечности часто выполняется путем сравнения ее результатов с количеством циклов нагружения до наступления разрушения. При этом реальные параметры нагружения могут существенно изменить выводы о причинах ускоренного накопления повреждений. Амплитудно-частотный анализ пульсационного режима работы трубопровода как единой гидравлической системы и, в частности, его оборудования является актуальной научно-технической задачей. Авторами рассмотрена возможность применения ПК Cassandra для оценки частотно-амплитудных колебательно-волновых процессов при нештатном режиме работы трубопоршневой поверочной установки (ТПУ) Daniel-4000. На примере одноразмерной имитационной модели установлено, что спектр частот волновых колебаний в жидкости содержит частоты, близкие к частоте собственных колебаний ТПУ. Помимо вращательно-колебательных возмущений, в запорно-регулирующей арматуре с различной периодичностью возникают поперечные нагрузки на шток затвора, и отмечается быстрое накопление усталостных малоцикловых повреждений в камере приема. К выходу из строя узлов ТПУ может привести как совместное воздействие этих факторов, так и каждый из них в отдельности. During operation, sometimes even minor pressure pulsations can cause significant mechanical oscillations (vibrations) of the pipeline and related equipment. It is obvious that if the frequency of transverse oscillations of the pipe caused by vibration of equipment is equal to the frequency of natural oscillations of the pipeline section, then resonant oscillations will occur, the amplitude of which will exceed the amplitude of exciting oscillations by tens of times. Vibration loads as a result of random or periodically recurring transients leads to a reduction in the safe life of defects, the formation of cracks in welds. Deterministic assessment of strength and durability is often performed by comparing its results with the number of loading cycles before failure occurs. At the same time, the actual loading parameters can significantly change the conclusions about the causes of accelerated damage accumulation. Amplitude - frequency analysis of the pulsation mode of operation of the oil pipeline as a single hydraulic system and its equipment, in particular, is an actual scientific and technical task. In this article, the opportunity of using the software IT complex Cassandra for diagnosis of the frequency-amplitude oscillatory wave processes during the emergency working mode of Daniel-4000 pipe piston installation (PPI) is being analyzed. The example of single-dimensional simulation data items shows that the frequency spectrum of wave oscillations in the liquid contains the oscillation frequency that is close to natural oscillation frequency of the PPI. In addition to rotational-oscillatory disturbances in the shutoff and control valves, transverse loads on the gate rod occur with different frequency and there is a rapid accumulation of fatigue low-cycle damage in the receiving chamber. The failure of the PPI nodes can be caused by both the combined effect of these factors and the action of each of them separately.
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Ren, Xiaoming, and Guangming Zhu. "A variable stiffness morphing skin: preparation and properties." Smart Materials and Structures 30, no. 12 (November 9, 2021): 125016. http://dx.doi.org/10.1088/1361-665x/ac32e8.
Повний текст джерелаАнотація:
Abstract In the course of flight, morphing skins play an important role in morphing aircrafts. Shape memory polymer (SMP) with variable stiffness performance is a good candidate material for skin. In this paper, a series of SMP morphing skins were prepared from hydro-epoxy resin, carboxyl-terminated butadiene acrylonitrile (CTBN) and maleic anhydride. By adjusting molecular weight and content of CTBN, in-plane properties and out-of-plane properties of morphing skins can be adjusted. Due to the in-plane tensile stress acting on the skin during flight, tensile test was carried out to study its in-plane performance. After testing, skin can resist maximum in-plane tensile strength of 63.7 MPa. As for the out-of-plane performance of the skin, shape memory test was studied in this paper. All morphing skins have 100% shape fixity rate (Rf) and fast shape recovery rate (Rr). When toughened by CTBN of 10% of 4000 molecular weight with a mass fraction, the skin can recover its out-of-plane deformed shape in 33 s. The SMP skins were proved to be a promising candidate for morphing skins.
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Choi, Kyungjun, Seong Jun Park, Mooncheol Won, and Cheol Hoon Park. "Soft fabric muscle based on thin diameter SMA springs." Smart Materials and Structures 31, no. 5 (April 19, 2022): 055020. http://dx.doi.org/10.1088/1361-665x/ac6550.
Повний текст джерелаАнотація:
Abstract This study proposes fabric muscles based on shape memory alloy (SMA) springs coiled with a thin diameter SMA wire of 80 μ m to improve heat dissipation under natural convection and forced air cooling. A new structure and its fabrication process are developed to create soft and flexible fabric muscles capable of supplying current and withstanding high external force, using a large number of thin SMA spring bundles. A total of 250 bundles of SMA springs weighing only 3.2 g constitute the fabric muscle that can lift a 1500 times-heavier mass, where each strand behaved like a muscle fiber. The fabric muscle generates a blocking force of up to 56.54 N and a power density of 2072 W kg−1. In addition, an air-cooling structure similar to a showerhead is proposed to further improve the actuation speed of the fabric muscles and maintain the flexibility of the fabric muscles. The fabric muscle with forced air cooling is cooled 40.5% faster than that with natural cooling. Finally, the results confirm that forced cooling can drive the muscle with a cycle of 5.5 s.
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Stauskis, Vytautas. "THE PECULIARITIES OF THE SOUND FIELD ENERGY DECAY IN A ROOM WITH THE USE OF DIFFERENT PULSED SOUND SOURCES/GARSO LAUKO ENERGIJOS SLOPIMO PATALPOJE YPATUMAI, NAUDOJANT SKIRTINGUS IMPULSINIUS GARSO ŠALTINIUS." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 5, no. 2 (April 30, 1999): 135–40. http://dx.doi.org/10.3846/13921525.1999.10531447.
Повний текст джерелаАнотація:
The paper deals with the differences between the energy created by four different pulsed sound sources, ie a sound gun, a start gun, a toy gun, and a hunting gun. A knowledge of the differences between the maximum energy and the minimum energy, or the signal-noise ratio, is necessary to correctly calculate the frequency dependence of reverberation time. It has been established by investigations that the maximum energy excited by the sound gun is within the frequency range of 250 to 2000 Hz. It decreases by about 28 dB at the low frequencies. The character of change in the energy created by the hunting gun differs from that of the sound gun. There is no change in the maximum energy within the frequency range of 63–100 Hz, whereas afterwards it increases with the increase in frequency but only to the limit of 2000 Hz. In the frequency range of 63–500 Hz, the energy excited by the hunting gun is lower by 15–30 dB than that of the sound gun. As frequency increases the difference is reduced and amounts to 5–10 dB. The maximum energy of the start gun is lower by 4–5 dB than that of the hunting gun in the frequency range of up to 1000 Hz, while afterwards the difference is insignificant. In the frequency range of 125–250 Hz, the maximum energy generated by the sound gun exceeds that generated by the hunting gun by 20 dB, that by the start gun by 25 dB, and that by the toy gun—by as much as 35 dB. The maximum energy emitted by it occupies a wide frequency range of 250 to 2000 Hz. Thus, the sound gun has an advantage over the other three sound sources from the point of view of maximum energy. Up until 500 Hz the character of change in the direct sound energy is similar for all types of sources. The maximum energy of direct sound is also created by the sound gun and it increases along with frequency, the maximum values being reached at 500 Hz and 1000 Hz. The maximum energy of the hunting gun in the frequency range of 125—500 Hz is lower by about 20 dB than that of the sound gun, while the maximum energy of the toy gun is lower by about 25 dB. The maximum of the direct sound energy generated by the hunting gun, the start gun and the toy gun is found at high frequencies, ie at 1000 Hz and 2000 Hz, while the sound gun generates the maximum energy at 500 Hz and 1000 Hz. Thus, the best results are obtained when the energy is emitted by the sound gun. When the sound field is generated by the sound gun, the difference between the maximum energy and the noise level is about 35 dB at 63 Hz, while the use of the hunting gun reduces the difference to about 20–22 dB. The start gun emits only small quantities of low frequencies and is not suitable for room's acoustical analysis at 63 Hz. At the frequency of 80 Hz, the difference between the maximum energy and the noise level makes up about 50 dB, when the sound field is generated by the sound gun, and about 27 dB, when it is generated by the hunting gun. When the start gun is used, the difference between the maximum signal and the noise level is as small as 20 dB, which is not sufficient to make a reverberation time analysis correctly. At the frequency of 100 Hz, the difference of about 55 dB between the maximum energy and the noise level is only achieved by the sound gun. The hunting gun, the start gun and the toy gun create the decrease of about 25 dB, which is not sufficient for the calculation of the reverberation time. At the frequency of 125 Hz, a sufficiently large difference in the sound field decay amounting to about 40 dB is created by the sound gun, the hunting gun and the start gun, though the character of the sound field curve decay of the latter is different from the former two. At 250 Hz, the sound gun produces a field decay difference of almost 60 dB, the hunting gun almost 50 dB, the start gun almost 40 dB, and the toy gun about 45 dB. At 500 Hz, the sound field decay is sufficient when any of the four sound sources is used. The energy difference created by the sound gun is as large as 70 dB, by the hunting gun 50 dB, by the start gun 52 dB, and by the toy gun 48 dB. Such energy differences are sufficient for the analysis of acoustic indicators. At the high frequencies of 1000 to 4000 Hz, all the four sound sources used, even the toy gun, produce a good difference of the sound field decay and in all cases it is possible to analyse the reverberation process at varied intervals of the sound level decay.