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Journal articles on the topic 'Compact excavator'
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1
Chomka, Grzegorz, and Michał Kondaszewski. "Construction project of a long reach compact excavator." Journal of Mechanical and Energy Engineering 4, no. 4 (April 20, 2021): 341–56. http://dx.doi.org/10.30464/jmee.2020.4.4.341.
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The purpose of thesis was to comprehensively develop the construction project of a long reach compact excavator. Optimal solution was selected and its frames were determined by carrying out classic structural calculations. Then, based on them, a preliminary three-dimensional model was designed in the CAD environment. The prototype was subjected to a series of verification calculations and simulation tests using the finite element method under typical, but also non-standard operating conditions. Then, the structure was optimized and then tested again. Next, technical documentation of the final version was created. In the final part of work, technical and operational parameters of designed compact excavator were summarized and the direction of further actions was determined. The thesis ended with a summary of the observations arose during its implementation.
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Wang, Yun Chao, Wen Jie Pang, and Mei Zhou. "Research on Digging Performance of Backhoe Hydraulic Excavator." Advanced Materials Research 718-720 (July 2013): 1673–76. http://dx.doi.org/10.4028/www.scientific.net/amr.718-720.1673.
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Digging performances of excavator is a key important index for evaluation of excavator. It is a very complex and heavy work to compute digging performance of excavator. So a compact hydraulic excavator model was built by ADAMS software. The theoretical maximum tool force of excavator was analyzed. For bucket digging mode, the maximum tool force were analyzed for boom cylinder seven positions during the whole working range and the effect of different factors were discussed. The practical maximum tool force was gained. The actual tool force variations were found through the analysis of simulation results. It provides the basis for design and improvement of excavator.
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Wallace, Kieran Andrew, and Wai Ming Cheung. "Development of a compact excavator mounted dust suppression system." Journal of Cleaner Production 54 (September 2013): 344–52. http://dx.doi.org/10.1016/j.jclepro.2013.04.048.
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Shin, Suk-Shin, Jong-Ho Noh, and Jong-Ho Park. "Stress analysis of bucket rotating part of the compact excavator." Journal of the Korean Society of Marine Engineering 37, no. 2 (March 31, 2013): 178–82. http://dx.doi.org/10.5916/jkosme.2013.37.2.178.
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Zhang, Liangjun, Jinxin Zhao, Pinxin Long, Liyang Wang, Lingfeng Qian, Feixiang Lu, Xibin Song, and Dinesh Manocha. "An autonomous excavator system for material loading tasks." Science Robotics 6, no. 55 (June 30, 2021): eabc3164. http://dx.doi.org/10.1126/scirobotics.abc3164.
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Excavators are widely used for material handling applications in unstructured environments, including mining and construction. Operating excavators in a real-world environment can be challenging due to extreme conditions—such as rock sliding, ground collapse, or excessive dust—and can result in fatalities and injuries. Here, we present an autonomous excavator system (AES) for material loading tasks. Our system can handle different environments and uses an architecture that combines perception and planning. We fuse multimodal perception sensors, including LiDAR and cameras, along with advanced image enhancement, material and texture classification, and object detection algorithms. We also present hierarchical task and motion planning algorithms that combine learning-based techniques with optimization-based methods and are tightly integrated with the perception modules and the controller modules. We have evaluated AES performance on compact and standard excavators in many complex indoor and outdoor scenarios corresponding to material loading into dump trucks, waste material handling, rock capturing, pile removal, and trenching tasks. We demonstrate that our architecture improves the efficiency and autonomously handles different scenarios. AES has been deployed for real-world operations for long periods and can operate robustly in challenging scenarios. AES achieves 24 hours per intervention, i.e., the system can continuously operate for 24 hours without any human intervention. Moreover, the amount of material handled by AES per hour is closely equivalent to an experienced human operator.
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Kolleth, Horst. "Practical considerations for developing an automatically driven open pit mining machine: Compact bucketwheel excavator." International Journal of Surface Mining, Reclamation and Environment 2, no. 1 (January 1988): 37–42. http://dx.doi.org/10.1080/09208118808944135.
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Niraula, Abinab, Shuzhong Zhang, Tatiana Minav, and Matti Pietola. "Effect of Zonal Hydraulics on Energy Consumption and Boom Structure of a Micro-Excavator." Energies 11, no. 8 (August 10, 2018): 2088. http://dx.doi.org/10.3390/en11082088.
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This paper investigates the effect of extra weight caused by the Direct Driven Hydraulics (DDH) in a micro-excavator. These projects are investigating the implementation of zonal or decentralized hydraulics for non-road mobile machinery (NRMM) and stationary industrial applications. The benefit of DDH is the combination of electric and hydraulic technologies in a compact package compared to conventional hydraulics, which enables a reduction of potential leakage points, flexible tubing, and boosting of the system efficiency due to switching to direct pump control instead of a loss-generating conventional valve-based control. In order to demonstrate these benefits for the excavator case, this paper proposes a system model approach to assess and predict energy consumption of the zonal hydraulics approach implemented with DDH in various working cycles, complemented by a structural analysis. The finite element analysis utilized for this demonstrated that the extra weight and selected location of DDH units do not negatively affect the structure of the excavator. Simulation results demonstrated that the energy consumption is approximately 15% higher with extra weight added by the three DDH units. Although approximately 20% more regeneration energy is produced, taking into account the regeneration energy, the increases in energy consumption are about 12%.
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Kim, Jun-Sik, Seung-Hyun Lee, and Jae-Won Lee. "The Characteristic of the Hydraulic Control System with Bleed-off Center Type of a Compact Excavator." Transactions of the Korean Society of Mechanical Engineers A 32, no. 2 (February 5, 2008): 119–26. http://dx.doi.org/10.3795/ksme-a.2008.32.2.119.
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Luo, You Xin, Yan Geng Li, Heng Shu Li, and Hui Jun Wen. "Research and Development of Multi-Function Excavator Drill with Hydraulic Rotary Cutting and Pneumatic Impacting." Applied Mechanics and Materials 34-35 (October 2010): 874–77. http://dx.doi.org/10.4028/www.scientific.net/amm.34-35.874.
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To solve the existing shortage of cutting drill, a multi-function excavator drill with hydraulic rotary cutting and pneumatic impact was invented on the base of market investigation, which is suitable for different rocks because of combining hydraulic rotary cutting with pneumatic impacting. If working on the soft rock, the new drill will turn off the pneumatic rock drill, replace the drill bit and only operate with the rotary power head, while on the hard rock it will operate efficiently with the rotary power head and the pneumatic rock drill. The new drill has many features, such as compact structure, the capacity of meeting a variety of drilling requirements, wider operating range, lower energy consumption, higher drilling efficiency, comfortable and flexible operation, and lower cost.
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Tiuremnov, I. S., and D. V. Fedorova. "Review of manufacturers'recommendations on technological capabilities of ejectable excavator vibroplates assessment during soil compaction." Russian Automobile and Highway Industry Journal 17, no. 5 (November 11, 2020): 562–73. http://dx.doi.org/10.26518/2071-7296-2020-17-5-562-573.
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Introduction. Add-on compactors for excavators (ACE hereinafter) are replaceable working equipment for excavators. They are used for soil compaction after the backfill of trenches, wells, foundation cavities and other “narrow spaces” of construction, as well as soil compaction at slopes of embankments and excavations.In practical use of ACE, builders face two challenges:to justify the choice of an ACE for soil compaction under given conditions determined by the soil type and moisture, layer thickness, and the required compaction factor; to determine the time required to compact soil with an ACE at a single point positional compaction to ensure the required compaction factor of a given type of soil in a layer of required thickness.The problems above require the information regarding technological capabilities of ACEs in different technological situations of soil compaction. The assessment of such technological capabilities of ACEs, at the same time, should take into account the ongoing transition to a new regulatory framework in Russia in the field of assessment indicators for the results of soil compaction in construction.Materials and methods. ACE technological capabilities review was conducted based on the information provided on the official websites of the largest Russian and foreign ACE manufacturers and suppliers.Conclusion. The analysis of information provided by ACE manufacturers and suppliers showed that most of that information is technical specifications of ACEs and excavators. There is almost no information on technological capabilities of ACEs. At the same time, ACE manufacturers and suppliers use ambiguous terminology (for example, “compaction volume”) in the assessment of technological capabilities.Practical value. Lack of information on technological capabilities of ACEs in various technological situations of soil compaction leads to errors in selection of an ACE model and its operation time during single point positional soil compaction, which increases the risk of under compaction and reduced service life of constructed objects. To solve this problem, the Construction and Road-Building Machinery Department of Yaroslavl State Technical University is developing a methodology for calculating the results of soil compaction with an ACE in different technological situations.
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Poderni, R. Yu, I. N. Klementyeva, and D. G. Lyapin. "SPECIFIC FEATURES OF INTERACTION OF A WORKING ORGAN OF A COMPACT BUCKET WHEEL EXCAVATOR WITH ROCK IN A ZONE OF THEIR FRICTIONAL CONTACT." Ugol’, no. 12 (December 8, 2016): 20–22. http://dx.doi.org/10.18796/0041-5790-2016-12-20-22.
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Xue, Long, Baichao Chen, Zhenjia Zhao, Zhaolong Dang, and Meng Zou. "Experimental Study of Torque Using a Small Scoop on the Lunar Surface." International Journal of Aerospace Engineering 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/8035456.
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Chinese missions to the moon are planned to sample the regolith and return it to the earth. Microscale excavators may be good candidates for these missions, as they would significantly reduce the launch mass. Thus, it is necessary to research the interaction between the scoop and the regolith being sampled. We present the development of a simple apparatus to measure excavation torque. All tests were conducted using TYII-2 regolith simulant with gravels. The test results show that, under loose regolith conditions, the penetrating angle and the bulk density had a great influence on the excavation torque, while the rotating speed had little effect. However, when the bulk density was compact, the rotating speed did influence the excavation torque. The excavation torque increased sharply when the scoop encountered the gravels; actually, some of the parameters will influence the value of the torque such as the diameter, quantity, and position and inbuilt depth of the gravels. When the excavation torque sharply increases, the operation should be immediately stopped and checked.
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Chetail, Gilles. "Flow Sharing System for Compact Excavators." Auto Tech Review 2, no. 6 (June 2013): 32–35. http://dx.doi.org/10.1365/s40112-013-0339-2.
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RalftoBaben. "The ‘Flying Wheel’: A concept not only for compact bucket wheel excavators." International Journal of Surface Mining, Reclamation and Environment 6, no. 3 (January 1992): 115–20. http://dx.doi.org/10.1080/09208119208944325.
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Wierzbicki, Damian, and Marcin Nienaltowski. "Accuracy Analysis of a 3D Model of Excavation, Created from Images Acquired with an Action Camera from Low Altitudes." ISPRS International Journal of Geo-Information 8, no. 2 (February 13, 2019): 83. http://dx.doi.org/10.3390/ijgi8020083.
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In the last few years, Unmanned Aerial Vehicles (UAVs) equipped with compact digital cameras, have become a cheap and efficient alternative to classic aerial photogrammetry and close-range photogrammetry. Low-altitude photogrammetry has great potential not only in the development of orthophoto maps but is also increasingly used in surveying and rapid mapping. This paper presents a practical aspect of the application of the custom homemade low-cost UAV, equipped with an action camera, to obtain images from low altitudes and develop a digital elevation model of the excavation. The conducted analyses examine the possibilities of using low-cost UAVs to deliver useful photogrammetric products. The experiments were carried out on a closed excavation in the town of Mince (north-eastern Poland). The flight over the examined area was carried out autonomously. A photogrammetric network was designed, and the reference areas in the mine were measured using the Global Navigation Satellite System-Real Time Kinematic (GNSS-RTK) method to perform accuracy analyses of the excavation 3D model. Representation of the created numerical terrain model was a dense point cloud. The average height difference between the generated dense point cloud and the reference model was within the range of 0.01–0.13 m. The difference between the volume of the excavation measured by the GNSS kinematic method and the volume measured on the basis of a dense point cloud was less than 1%. The obtained results show that the application of the low-cost UAV equipped with an action camera with a wide-angle lens, allows for obtaining high-accuracy images comparable to classic, compact digital cameras.
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Yoshioka, Nobuto. "Mission-Task Support Aspects of Planetary Rover for Surface Analysis." Journal of Robotics and Mechatronics 12, no. 4 (August 20, 2000): 438–42. http://dx.doi.org/10.20965/jrm.2000.p0438.
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As an extension to space robotics technology, the National Space Development Agency of Japan (NASDA) has been examining possible scenarios for unmanned planetary explorations. The paper discusses the roles of planetary rovers in terms of mission support aspects during presumed lunar-surface robotics tasks, and then describes a Compact Payload-Interface-Device (CPID) that acts as a common gateway for detachable instruments. A surface excavation tool is also designed and evaluated for its ""mechanics-soil interaction"" as one example of system design.
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Cardu, Marilena, Ettore Catanzaro, Angelo Farinetti, Daniele Martinelli, and Carmine Todaro. "Performance Analysis of Tunnel Boring Machines for Rock Excavation." Applied Sciences 11, no. 6 (March 21, 2021): 2794. http://dx.doi.org/10.3390/app11062794.
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The study takes into account different classes of tunnel boring machines (TBM), with the aim of identifying correlation models which are meant to estimate, at a preliminary design phase, the construction time of a tunnel and to evaluate the mechanical and operational parameters of the TBMs, starting from the knowledge of the tunnel length and the excavation diameter. To achieve this goal, first of all a database was created, thanks to the collection of the most meaningful technical parameters from a large number of tunnels; afterwards, it was statistically analyzed through Microsoft Excel. In a first phase, forecasting models were identified for the three types of machines investigated, separately for compact rocks (open TBM) and fractured rocks (single and double shield TBM). Then, the mechanical parameters collected through the database were analyzed, with the aim of obtaining models that take into account, in addition to the type of TBM, the geological aspect and the type of rock characterizing the rock mass. Finally, the validation of the study was proposed in a real case, represented by the Moncenisio base tunnel, a work included in the new Turin–Lyon connection line. The estimated values were compared with the real ones, in order to verify the accuracy of the experimental models identified.
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Harrison, R. M., and N. Christie et al. "Excavations at Amorium: 1992 Interim Report." Anatolian Studies 43 (December 1993): 147–62. http://dx.doi.org/10.2307/3642972.
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August 1992 marked the sixth season of survey and excavation at the east Phrygian site of Amorium, located 170 km. south-west of Ankara. Excavation has so far sampled only a tiny part of what was in Roman and Byzantine times an extensive urban site, but results have consistently revealed that an exciting range of data can be drawn from this largely unexplored centre. Indeed, despite evident modern robbing for stone, the trenched areas have revealed that substantial zones may remain archaeologically intact.The ancient site of Amorium comprised two distinct fortified zones: a compact upper town, and a larger lower town, part of which is now overlain by the modern village of Hisarköy. A particular aim of the excavations so far carried out at Amorium has been to define the relationship between these two urban areas in the overall occupational sequence, with special interest placed on elucidating the transitional phase from the Early to Middle Byzantine period—a period in Amorium's long history which is fairly well documented by both Byzantine and Arab sources.
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Gifford-Gonzalez, Diane P., David B. Damrosch, Debra R. Damrosch, John Pryor, and Robert L. Thunen. "The Third Dimension in Site Structure: An Experiment in Trampling and Vertical Dispersal." American Antiquity 50, no. 4 (October 1985): 803–18. http://dx.doi.org/10.2307/280169.
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AbstractTwo measured and weighed assemblages of lithic debitage were subjected to human treadage, one set on a compact sandy silt (“loam”) substrate, the other on unconsolidated sand. The assemblages were excavated, plotted in three dimensions, and documented for damage. Downward migration of pieces at the loam site was minimal: fracture of small pieces was the dominant damage pattern. Most sand site pieces migrated to 3-8 cm depth; vertical distribution of pieces approximated a normal curve, and edge-damage to larger pieces was the dominant damage pattern. Vertical distribution of artifacts at the sand site approximated a pattern observed in two other trampling experiments and a number of archaeological occurrences. Factors influencing these distributions are discussed.
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Keever, Gary J., and G. S. Cobb. "Plant Response to Container Planting Method and Media." Journal of Environmental Horticulture 8, no. 4 (December 1, 1990): 189–92. http://dx.doi.org/10.24266/0738-2898-8.4.189.
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Abstract Shoot dry weight and relative root density of Ilex crenata Thunb. ‘Compacta’ and Rhododendron obtusum (Lindl.) Planch. ‘Hino Crimson’ were greater when liners were transplanted into holes with a core removed (excavated) compared to holes formed by compression (dibbled). Growth index, relative root density, and shoot dry weight increased as the percent pine bark in the growth media increased from 50% to 80 or 90% pine bark with holly and from 50% to 90% pine bark with azalea. Bulk density decreased and air porosity and irrigation frequency increased as the percent pine bark in pine bark:sandy loam container media increased from 50% to 100%. In a second experiment, root density and shoot dry weight of Ilex crenata Thunb. ‘Helleri’, but not Rhododendron × ‘Trouper’, were greater in pine bark and pine bark-sandy loam media when the planting hole was excavated rather than dibbled. Plant growth of the 2 species in peat-based media was not influenced by planting method.
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Geier, J. E., and M. Hood. "The Effect on Cutting Tool Forces of Pre-Weakening a Rock Surface by Waterjet Kerfing." Journal of Engineering for Industry 111, no. 1 (February 1, 1989): 1–6. http://dx.doi.org/10.1115/1.3188727.
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Empirical models are developed to describe the influence on the cutting process of preweakening a rock, by cutting a series of parallel kerfs in the surface with high pressure waterjets, prior to excavating the rock with a polycrystalline diamond compact (PDC) drag bit. These models show that both the bit cutting force and the bit normal force are reduced substantially (by as much as a factor of four) when the spacing and the depth of the kerfs is appropriate to the depth of cut taken by the bit. The mechanical specific energy, or the mechanical energy applied to the bit to excavate a unit volume of rock, is also reduced dramatically when the rock is prekerfed.
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Singh, Vandana, and Manager Rajdeo Singh. "Characterization of Corrosion Behavior of Archaeological Iron Spear from Sanur (300 BC – 50 AD) – A Megalithic Site in Southern India." Acta Chemica Malaysia 3, no. 1 (June 1, 2019): 21–28. http://dx.doi.org/10.2478/acmy-2019-0003.
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Abstract This investigation deals with the chemical composition and microstructural analysis of the iron object, a spear excavated from Sanur, Tamil Nadu- a megalithic site dated 300 B.C. to 50 A.D. Phase analysis and microstructural examination were carried using XRD, optical and variable pressure scanning electron microscope (VP-SEM). Optical micrograph shows the equiaxed grain structure along with the Newman bands. Formation of Newman bands suggests that the original artifact was forged at high temperature followed by cooling, although not so rapid to produce the marked hardening. The absence of carbides at the grain boundary, within the grains and lower value of micro-hardness indicates that the iron spear was not subjected to the carburizing treatment. Results of corrosion characterization revealed that deterioration of excavated iron artifact is associated with the presence of chlorine in corrosion products. However, compact nature of the outer rust (goethite) was helpful in protecting the object. The formation of goethite [ ∝-FeOOH] layer may prevent the iron matrix suffering from attacks by other environmental factors due to its good continuity. In addition, less aerated environment of storage and no history of any cleaning of object were also helpful in preventing the iron spear from further deterioration.
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Pozo-Antonio, Jose Santiago, Beatriz Comendador Rey, Lara Alves Bacelar, and Pablo Barreiro. "Methodological Approach (In Situ and Laboratory) for the Characterisation of Late Prehistoric Rock Paintings—Penedo Gordo (NW Spain)." Minerals 11, no. 6 (May 22, 2021): 551. http://dx.doi.org/10.3390/min11060551.
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This paper draws on the study of the prehistoric art site of Penedo Gordo (NW Spain) resulting from a collaborative interdisciplinary research. One of its primary goals was to design and put into practice a multi-analytical protocol for characterising prehistoric rock paintings, combining in situ and laboratory analytical techniques. Thus, following the archaeological assessment of the site, the panels exhibiting red paintings were analysed by colour spectrophotometry and portable Raman spectroscopy. Analytical techniques were applied to a collection of samples exhumed from the excavation that simultaneously took place on site. These included three red accretions on different substrates (compact soil, white quartzite and grey quartzite) and stone fragments representative of the outcrop’s petrographic variability, aiming to determine their mineralogical composition, texture and study the stone-paint boundaries. Moreover, colouring materials exhumed from the excavation and collected in the immediate surroundings of the rock outcrop were analysed in order to scrutinise the provenience rock art’s raw materials. Laboratory analysis consisted of stereomicroscopy, X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. One of the major outcomes was the discovery of a drop of red pigment preserved in an archaeological layer associated with Late Neolithic/Copper Age material remains.
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Drzewiecki, Mariusz. "The Kushite temple in Soniyat after the 2016 season." Polish Archaeology in the Mediterranean 26, no. 1 (July 9, 2018): 326–36. http://dx.doi.org/10.5604/01.3001.0012.1792.
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Archaeological fieldwork in the Kushite temple in Soniyat (Tergis 40) was conducted from 1997 to 2001 with an additional short season in 2013. A team supervised by Bogdan Żurawski returned to the site in 2016 to continue the excavation of the southern section of the complex. Remains of substantial mud-brick architecture were discovered together with large quantities of small finds (potsherds and objects made of metal, stone and faience) and faunal remains. A compact layer of Nile alluvial deposits, about 0.10 m thick, covering the remains represented evidence most probably of a flood. A single stone column was visible at that level. The spatial distribution of the discovered architectural features matches the temple orientation; they can be interpreted as the remains of a pylon with an entrance flanked by columns
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Brown, A. C., and E. R. Trueman. "Burrowing Behaviour and Cost in the Sandy-Beach Oniscid Isopod Tylos Granulatus Krauss, 1843." Crustaceana 69, no. 4 (1996): 425–37. http://dx.doi.org/10.1163/156854096x01014.
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AbstractTylos granulatus is an isopod living above the driftline on sandy shores, burrowing to depths of up to a metre or more. Burrowing has been investigated by analyzing video recordings and traces from isotonic and isometric transducers. In crawling, all seven pairs of pereiopods operate in a similar manner and display metachronal rhythm, while in burrowing pereiopods 1 to 3 do the digging, pairs 4 to 6 compact the excavated sand, and pair 7 pushes the bolus behind the animal. Movements of the head also play a significant role in burrowing. Clockwise or anticlockwise partial rotation occurs during burrowing, which takes place in a stepwise progression. With a Burrowing Rate Index of 3, the animal must be considered a powerful burrower, while the energy cost of burrowing is surprisingly low at some 0.3 J m-1.
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Maharjan, Rajib, and Vivek Shrestha. "Analysis of One Bay Residential Building with Combined RCC Frame and Load Bearing Wall Structures." Journal of the Institute of Engineering 13, no. 1 (June 22, 2018): 117–24. http://dx.doi.org/10.3126/jie.v13i1.20356.
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The major purpose of this study is to justify construction method of a hybrid structure in core area with construction complexity due unsafe excavation conditions and tries to define its rigidity and strength. Both RCC and Frame structure transfer same load to ground through foundation but the transfer mechanism varies. In some practical condition, building construction should be carried out in compact areas with unsafe adjoining building where adequate excavation for foundation cannot be carried out. In such cases, one bay hybrid structure is proposed for construction with combined RCC frame structure and load bearing walls. In these combined cases, both structures works as same unit to transfer building load but the transfer pattern varies. The variable load transfer pattern is due to discontinuity in structural system which also effect on seismic response of the building. The placement of a masonry load bearing structure in RCC frame structure varies design of all structural components of the building. To study actual behavior of hybrid structure in various load condition and introducing cost minimization techniques of buildings structural analysis was carried using ETABS 2016 with composite structural arrangement and with induction of load bearing wall as structural component. By which seismic behavior of building in both cases was obtained as well as reduction in rebar percentage and dimensional reduction of structural components can be achieved.Journal of the Institute of Engineering, 2017, 13(1): 117-124
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Moriya, Toru, Hiroko Miyahara, Motonari Ohyama, Masataka Hakozaki, Mirei Takeyama, Hirohisa Sakurai, and Fuyuki Tokanai. "A Study of Variation of the 11-yr Solar Cycle before the onset of the Spoerer Minimum based on Annually measured 14C Content in tree Rings." Radiocarbon 61, no. 6 (November 22, 2019): 1749–54. http://dx.doi.org/10.1017/rdc.2019.123.
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ABSTRACTProxy-based observations of solar activity in the past have revealed long-term variations, such as the Gleissberg cycle (~88 yr), de Vries cycle (~200 yr), and the Hallstatt cycle (~2000 yr). Such long-term variations of solar activity sometimes cause the disappearance of sunspots for several decades. Currently, solar activity is becoming weaker, and there is a possibility that another long-term sunspot minimum could occur. However, the detailed mechanism of the weakening in solar activity is unknown, and the prediction of solar activity is ambiguous. In this study, we investigate the transitions of solar cycle length before the onset of the Spoerer Minimum, the longest grand minimum in the past 2000 yr. We measured the 14C content in an asunaro tree (Thujopsis dolabrata) excavated at Shimokita Peninsula from 1368–1420 CE using the compact AMS system at Yamagata University. It is found that the solar cycle lengthened to be 14–16 yr from 2 cycles before the onset of the Spoerer Minimum.
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Frolov, A., G. Rendle, A. Kreskowski, M. Kaisheva, B. Froehlich, and V. Rodehorst. "TOWARDS FREE-VIEWPOINT VIDEO CAPTURE IN CHALLENGING ENVIRONMENTS FOR COLLABORATIVE & IMMERSIVE ANALYSIS." International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLIII-B2-2021 (June 28, 2021): 419–26. http://dx.doi.org/10.5194/isprs-archives-xliii-b2-2021-419-2021.
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Abstract. The ability to capture and explore complex real-world dynamic scenes is crucial for their detailed analysis. Tools which allow retrospective exploration of such scenes may support training of new employees or be used to evaluate industrial processes. In our work, we share insights and practical details for end-to-end acquisition of Free-Viewpoint Videos (FVV) in challenging environments and their potential for exploration in collaborative immersive virtual environments. Our lightweight capturing approach makes use of commodity DSLR cameras and focuses on improving both density and accuracy of Structure-from-Motion (SfM) reconstructions from small sets of images under difficult conditions. The integration of captured 3D models over time into a compact representation allows for efficient visualization of detailed FVVs in an immersive multi-user virtual reality system. We demonstrate our workflow on a representative acquisition of a suction excavation process and outline a use-case for exploration and interaction between collocated users and the FVV in a collaborative virtual environment.
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Shao, W., Xing Sheng Li, Yong Sun, and Han Huang. "Laboratory Comparison of SMART*CUT Picks With WC Picks." Advanced Materials Research 1017 (September 2014): 323–28. http://dx.doi.org/10.4028/www.scientific.net/amr.1017.323.
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Application of polycrystalline diamond compact (PDC) based cutting tools for hard rock excavation in mining and construction industries has increased significantly in recent years due to their super hardness, superb thermal conductivity and long life durability. Super Material Abrasive Resistant Tool (SMART*CUT) technology has been developed by CSIRO (Commonwealth Scientific and Industrial Research Organisation) in the last 15 years, which includes the replacement of tungsten carbide (WC) tips of the conventional picks with thermally stable diamond composite (TSDC) tips, attachment of the TSDC tips to steel tool bodies with CSIRO’s worldwide patented bonding technology. The wear characteristics of TSDC cutting elements have been investigated previously. In this paper, the preliminary results of cutter forces and resultant angle of SMART*CUT picks were compared with that of traditional WC picks. A tri-axial force dynamometer and a data acquisition system were used to measure the cutter forces. Besides, the cutting area temperature during cutting process was continuously measured by a FLIR SC7600M thermal infrared camera and the recorded data were processed by Altair Software.
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Li, Ming, Gang Lin, Wei Zhou, Xianbiao Mao, Lianying Zhang, and Rongrong Mao. "Experimental Study on Dynamic Tensile Failure of Sandstone Specimens with Different Water Contents." Shock and Vibration 2019 (September 9, 2019): 1–15. http://dx.doi.org/10.1155/2019/7012752.
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Understanding the effect of water saturation on dynamic failure of rocks is of great importance to tunnel excavation at water-rich coal mines and prevention of rock bursts by water injection. Dynamic Brazilian disc tests are performed to study mechanical behaviour of sandstones in this paper. The results indicate that water saturation significantly weakens the dynamic tensile strength of sandstones and increases the specimen strain at which the specimen fails. The damage degree of sandstones reduces gradually with increasing water contents. Failure of the sandstone specimen includes the crack initiation at the center of the specimen, macroscopic crack propagation, and stretch of the macroscopic crack through the specimen. In addition, parallel macroscopic crack propagation is found in the specimen with a low water content. From the observation of fracture sections, microstructures are compact in the specimen with high water contents. This is due to the swell of the kaolinite in the specimen after water saturation. The failure mechanism of microstructures is typical brittle failure in the specimen with a high water content, whereas ductile fracture is found in the specimen with a low water content. Different failure processes of microstructures lead to the differences between mechanical properties and macroscopic failure characteristics of the specimens with various water contents.
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Acharya, Dr Priyanka, Dr Rashmi Paramashiviah, Dr Prabhuji MLV, and Dr Shaeesta Khaleelahmed Bhavikatti. "Osseodensification- the ideal path to accomplish complete osseointegration." RGUHS Journal of Dental Sciences 11, no. 1 (2019): 89–95. http://dx.doi.org/10.26715/rjds.11_1_3.
Full textAbstract:
Implant stability is a prerequisite for successful implant osseointegration. Over the years, implant site preparation has been refined taking into consideration the fact that, the bone is a viable tissue. Even minor alterations in the steps of osteotomy like overheating, increased pressure etc. could lead to failure in osseointegration. This could be due to an alteration in the microvascular dynamics. Implant site osteotomies have been prepared using conventional drills since several decades. These drills are designed so as to excavate the native bone to create room for the implant to be placed. Contrary to that, a new technique is introduced which instead of excavating the bone tissue compacts and autografts the bone in an outwardly expanding directions from the osteotomy. This novel approach termed osseodensification, aids to preserve the bony bulk, increase primary stability through densification of the osteotomy walls, hastens the healing and facilitates ridge expansion. This narrative review focuses on the new bone drilling concept, namely osseodensification and its advantages over the standard subtractive drilling techniques.
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de Smet, T. S., M. E. Everett, C. J. Pierce, D. L. Pertermann, and D. B. Dickson. "Electromagnetic induction in subsurface metal targets: Cluster analysis using local point-pattern spatial statistics." GEOPHYSICS 77, no. 4 (July 1, 2012): WB161—WB169. http://dx.doi.org/10.1190/geo2011-0391.1.
Full textAbstract:
The detection and localization of statistically significant spatial clustering of buried metal artifacts for applications, including archaeological, environmental site assessment, and civil infrastructure mapping, can be performed reliably, inexpensively, and noninvasively using transient electromagnetic (EM) geophysics. The local [Formula: see text] statistic based on a weighted spatial autocorrelation were used to detect and localize statistically significant clustering of buried metal objects from gridded electromagnetic responses acquired at a seeded control site and at an active historical archaeological site in Paint Rock, Texas. This statistic compares the local EM millivolt response values about point [Formula: see text] radially to the global mean and variance to calculate the [Formula: see text] statistic as a standard variate at various length scales, which can therefore be assessed for significance. Because the local [Formula: see text] statistic compares local to global averages, it spatially compacts the amplitude response signal of the EM data. The resulting spatial cluster maps conformed well to the known distribution of metal targets buried at the control site, and enabled a successful excavation strategy with a significant reduction in false positives encountered at the archaeological site, when compared with more traditional methods.
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Vanderburgh, S., and M. C. Roberts. "Depositional systems and seismic stratigraphy of a Quaternary basin: north Okanagan Valley, British Columbia." Canadian Journal of Earth Sciences 33, no. 6 (June 1, 1996): 917–27. http://dx.doi.org/10.1139/e96-069.
Full textAbstract:
Seismic and core data from north Okanagan Valley, a deep (~700 m of fill), elongate (~3 km wide by 45 km long) basin located in the Cordillera of south-central British Columbia, reveal a thick sequence of fine and coarse elastics. The architecture of the basin fill was delineated using 16 km of high-resolution, reflection seismic profiles, and 30 lithologic logs. Using a depositional systems approach, four systems were identified: subglacial fluvial, glaciolacustrine, alluvial fan, and channel. The subglacial fluvial system consists of a basal suite of compact, stratified to poorly stratified coarse clastics deposited beneath glacial ice under high hydrostatic pressure. Older sediments were almost completely excavated from the basin fill during periods of maximum subglacial flow during Late Wisconsinan glaciation. One of the outcomes of this study is that it lends support to the notion that Late Wisconsinan glaciers were capable of almost totally eroding older Pleistocene basin deposits while depositing thick sequences of subglacial fluvial sediments. During deglaciation, the basin was occupied by a lake in which laminated silt and clay were deposited (glaciolacustrine system). The wedge-shaped alluvial fan system interfingers with the finer clastics of the basin fill. Incised into the upper part of the basin fill are channel sediments forming the channel depositional system. Two stages in the evolution of the north Okanagan basin were identified: in the first stage (~10 ka), lake sediments were rapidly accumulating coeval with the formation of alluvial fans and fan deltas; the second stage shows the present-day architecture of the basin fill.
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Campbell, Jacqueline, Panagiotis Sidiropoulos, and Jan-Peter Muller. "IR SPECTRAL MAPPING OF THE MARTIAN SOUTH POLAR RESIDUAL CAP USING CRISM." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (June 17, 2016): 71–75. http://dx.doi.org/10.5194/isprsarchives-xli-b7-71-2016.
Full textAbstract:
Polycyclic aromatic hydrocarbons (PAHs) are considered to be important in theories of abiogenesis (Allamandola, 2011) . There is evidence that PAHs have been detected on two icy Saturnian satellites using the Visual and Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft (Cruikshank et al., 2007). The hypothesised presence of PAHs in Mars south polar cap has not been systematically examined even though the Mars south polar cap may allow the preservation of organic molecules that are typically destroyed at the Martian surface by UV radiation (Dartnell et al. 2012). This hypothesis is supported by recent analyses of South Polar Residual Cap (SPRC) structural evolution (Thomas et al., 2009) that suggest the possibility that seasonal and long term sublimation may excavate dust particles from within the polar ice. Periodic sublimation is believed to be responsible for the formation of so-called “Swiss Cheese Terrain”, a unique surface feature found only in the Martian south polar residual cap consisting of flat floored, circular depressions (Byrne, 2009). We show the first examples of work towards the detection of PAHs in Swiss Cheese Terrain, using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), on board NASA’s Mars Reconnaissance Orbiter (MRO). CRISM is designed to search for mineralogical indications of past and present water, thus providing extensive coverage of the south polar cap. In this work, we discuss whether CRISM infrared spectra can be used to detect PAHs in Swiss Cheese Terrain and demonstrate a number of maps showing shifts in spectral profiles over the SPRC.
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Campbell, Jacqueline, Panagiotis Sidiropoulos, and Jan-Peter Muller. "IR SPECTRAL MAPPING OF THE MARTIAN SOUTH POLAR RESIDUAL CAP USING CRISM." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLI-B7 (June 17, 2016): 71–75. http://dx.doi.org/10.5194/isprs-archives-xli-b7-71-2016.
Full textAbstract:
Polycyclic aromatic hydrocarbons (PAHs) are considered to be important in theories of abiogenesis (Allamandola, 2011) . There is evidence that PAHs have been detected on two icy Saturnian satellites using the Visual and Infrared Mapping Spectrometer (VIMS) on the Cassini spacecraft (Cruikshank et al., 2007). The hypothesised presence of PAHs in Mars south polar cap has not been systematically examined even though the Mars south polar cap may allow the preservation of organic molecules that are typically destroyed at the Martian surface by UV radiation (Dartnell et al. 2012). This hypothesis is supported by recent analyses of South Polar Residual Cap (SPRC) structural evolution (Thomas et al., 2009) that suggest the possibility that seasonal and long term sublimation may excavate dust particles from within the polar ice. Periodic sublimation is believed to be responsible for the formation of so-called “Swiss Cheese Terrain”, a unique surface feature found only in the Martian south polar residual cap consisting of flat floored, circular depressions (Byrne, 2009). We show the first examples of work towards the detection of PAHs in Swiss Cheese Terrain, using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), on board NASA’s Mars Reconnaissance Orbiter (MRO). CRISM is designed to search for mineralogical indications of past and present water, thus providing extensive coverage of the south polar cap. In this work, we discuss whether CRISM infrared spectra can be used to detect PAHs in Swiss Cheese Terrain and demonstrate a number of maps showing shifts in spectral profiles over the SPRC.
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Jin, Hong, Jing Zhao, Siqi Liu, and Jian Kang. "Climate Adaptability Construction Technology of Historic Conservation Areas: The Case Study of the Chinese–Baroque Historic Conservation Area in Harbin." Sustainability 10, no. 10 (September 20, 2018): 3374. http://dx.doi.org/10.3390/su10103374.
Full textAbstract:
In recent years, the conflict between human activities and the natural environment has led to global warming and extreme weather, which has provoked people into thinking about the climate adaptability of buildings. Historical blocks are usually built and designed based on the social environment and climatic conditions at that time; therefore, they generally contain the construction techniques relevant to dealing with the local climate. The study aims to study the microclimate characteristics of a historic conservation area in a severe cold region and to explore how it attempted to achieve climate adaptation. Taking the Chinese–Baroque historic conservation area in Harbin as an example, this paper analyzed and studied the climate adaptability technology and excavated the suitable technology for the block to deal with a severe cold climate through research, field measurements, and numerical simulation. The results showed that compared with a certain modern urban area in the city, the Chinese–Baroque historic conservation area had better ability to resist wind and cold. The compact layout of the block could reduce heat loss and keep out the cold by effectively resisting the cold wind from permeating inside. Compared with the T-shaped and L-shaped courtyards, the rectangular courtyard occupies the largest proportion and a rectangular courtyard enclosed by buildings on all sides had better windbreak performance. Furthermore, when the courtyard space was enclosed by four sides and the courtyard width was the same, when the plane aspect ratio was smaller, the maximum wind speed of the inner courtyard was smaller. The squares in the block had a good performance in cold resistance. At the same scale, the higher the degree of enclosure of the square, the lower the internal wind speed. This study will provide a reference for urban planning and architectural design in severe cold regions.
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Fuente, A., S. P. Treviño-Morales, T. Alonso-Albi, A. Sánchez-Monge, P. Rivière-Marichalar, and D. Navarro-Almaida. "Probing the kinematics and chemistry of the hot core Mon R2 IRS 3 using ALMA observations." Monthly Notices of the Royal Astronomical Society 507, no. 2 (August 2, 2021): 1886–98. http://dx.doi.org/10.1093/mnras/stab2216.
Full textAbstract:
ABSTRACT We present high angular resolution 1.1 mm continuum and spectroscopic Atacama Large Millimeter/submillimeter Array observations of the well-known massive protocluster Mon R2 IRS 3. The continuum image at 1.1 mm shows two components, IRS 3 A and IRS 3 B, that are separated by ∼0.65 arcsec. We estimate that IRS 3 A is responsible of ∼80 per cent of the continuum flux, being the most massive component. We explore the chemistry of IRS 3 A based on the spectroscopic observations. In particular, we have detected intense lines of S-bearing species such as SO, SO2, H2CS, and OCS, and of the complex organic molecules (COMs) methyl formate (CH3OCHO) and dimethyl ether (CH3OCH3). The integrated intensity maps of most species show a compact clump centred on IRS 3 A, except the emission of the COMs that is more intense towards the near-IR nebula located to the south of IRS 3 A, and HC3N whose emission peak is located ∼0.5 arcsec NE from IRS 3 A. The kinematical study suggests that the molecular emission is mainly coming from a rotating ring and/or an unresolved disc. Additional components are traced by the ro-vibrational HCN ν2 = 1 3→2 line which is probing the inner disc/jet region, and the weak lines of CH3OCHO, more likely arising from the walls of the cavity excavated by the molecular outflow. Based on SO2 we derive a gas kinetic temperature of T$_k\, \sim$ 170 K towards the IRS 3 A. The most abundant S-bearing species is SO2 with an abundance of ∼ 1.3 × 10−7, and χ(SO/SO2) ∼ 0.29. Assuming the solar abundance, SO2 accounts for ∼1 per cent of the sulphur budget.
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Manekar, Ganesh, Dipankar Shome, and Mukund Chaudhari. "Modified ground support with alternative fill material for ground control at munsar underground manganese mine of moil limited, India." New Trends in Production Engineering 2, no. 1 (October 1, 2019): 69–77. http://dx.doi.org/10.2478/ntpe-2019-0007.
Full textAbstract:
Abstract MOIL Limited is operating 7 underground and 3 opencast mines in central India and producing annually more than 1.3 million tonnes of various grades of manganese ore. The underground mines are operating at shallow – 90 m at Munsar mine to moderate – 353 m at Balaghat mine below the surface with horizontal cut and fill (HCF) or its variant method of stoping with post filling by hydraulic sand stowing. The Munsar mine is being worked underground since 1903. The opencast mining is presently stopped. The ore body below the opencast quarry is geological continuity of the area excavated in past by opencast method of mining. The underground mining is done through the adit in three levels i.e. 270’L, 220’L, 170’L and by incline in western part of the property at 70’L. The horizontal drift development has been developed in the manganese ore body with sill drive of 5 m above the sill pillar in lower level at 70’L and barrier pillar of 5 m thickness is left for protection of upper level at 170’L. Valuable mineral has been locked in sill pillar and therefore rock mechanics investigations have been carried out. On the basis of study now the drift development has been carried out in footwall rock at 70’L, (-) 30’L and below levels and it has improved the minable manganese ore by about 20%. In this modified HCF stope design, an alternative fill material in place of sand, which has been developed in house by use of overburden (OB) material after treatment, has been used for hydraulic stowing. The experimental trials find out that the alternative fill material of OB is more compact and forms a non-expansion floor for the men and machines in the stope. This will certainly help in the introduction of mobile underground mining equipment for drilling in the stopes and mechanical mucking, transportation and loading of the ROM. The paper presents rock mechanics investigations and future use of alternative fill material of overburden material after heat treatment for better safety and productivity at Munsar Mine of MOIL.
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Karmanov, V. N. "Vadniur I/7 — the final Neolithic and Eneolithic site of the Vychegda River." VESTNIK ARHEOLOGII, ANTROPOLOGII I ETNOGRAFII, no. 4 (51) (November 27, 2020): 63–72. http://dx.doi.org/10.20874/2071-0437-2020-51-4-6.
Full textAbstract:
The author presents the results of his own survey of the Vadniur I settlement carried out in 2017. The site is located on the right bank of the Vychegda River in the Syktyvkar city, the Komi Republic (north-eastern Europe). The danger of destruction of the site by the river erosion erged the comprehensive excavation of the total area of 210.5 m2. This has made it possible to preserve the historical and cultural information from the site and to obtain new data for the study of the Neolithic and Eneolithic cultures of north-eastern Europe. Based on stratigraphy, planigraphy and comparative-typological method, two complexes of different periods — Vadniur I/7A and Vadniur I/7B — have been identified. The former includes the remains of a rectangular 11x5 m dwelling with the total area of ca. 55 m2, with three hearths (nos. I, II and IV) and two horizontal ventilation channels (nos. I and II). The construction is associated with a ca. 8.5 m2 section of redeposited cultural layer containing artefacts, which is probably the result of cleaning of the living space in ancient times. The dwelling complex includes 428 stone items, fragments of two ceramic pots and three ceramic objects, small unidentifiable fragments of calcified bones. According to two radiocarbon measurements, the Vadniur I/7A complex dates to the first half of the 4th mil. BC. This data, together with construction features, technical and typological charac-teristics of ceramics and flint tools, allow attributing it to the early period of the Chuzhyael'skaya Culture in north-eastern Europe. Currently, Vadniur I/7A is the oldest structure of this type in Northern Eurasia. The research opens new per-spectives for the study of genesis of the Chuzh"yael'skaya Culture, which is also associated with searching for sources of origin of housebuilding, flint knapping and pottery traditions unique for the northeast of Europe. The Vadniur I/7B complex has been identified as a compact cluster of ceramic vessel fragments and few flint artefacts. They were related to the traces of hearth no. III and together may represent remains of a short-term camp. The comparative-typological method allows to identify it as a site of the Choynovtinskaya Culture of the Eneolithic Volosovo-Garinskaya cultural com-munity of the 3rd — first half of the 2nd mil. BC.
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Rigliaco, E., R. Gratton, Á. Kóspál, D. Mesa, V. D’Orazi, P. Ábrahám, S. Desidera, et al. "The circumstellar environment of EX Lupi: SPHERE and SINFONI views." Astronomy & Astrophysics 641 (September 2020): A33. http://dx.doi.org/10.1051/0004-6361/202038337.
Full textAbstract:
Context. EX Lup is a well-studied T Tauri star that represents the prototype of young eruptive stars known as EXors. They are characterized by repetitive outbursts that are due to enhanced accretion from the circumstellar disk onto the star. In this paper, we analyze new adaptive optics imaging and spectroscopic observations to study EX Lup and its circumstellar environment in near-infrared in its quiescent phase. Aims. We aim to provide a comprehensive understanding of the circumstellar environment around EX Lup in quiescence, building upon the vast store of data provided by the literature. Methods. We observed EX Lup in quiescence with the high contrast imager SPHERE/IRDIS in the dual-beam polarimetric imaging mode to resolve the circumstellar environment in near-infrared scattered light. We complemented the data with earlier SINFONI spectroscopy, which was also taken in quiescence. Results. We resolve, for the first time in scattered light, a compact feature around EX Lup azimuthally extending from ~280° to ~360° and radially extending from ~0.3′′ to ~0.55′′ in the plane of the disk. We explore two different scenarios for the detected emission. The first one accounts for the emission as coming from the brightened walls of the cavity excavated by the outflow whose presence was suggested by ALMA observations in the J = 3−2 line of 12CO. The second attributes the emission to an inclined disk. In this latter case, we detect, for the first time, a more extended circumstellar disk in scattered light, which shows that a region between ~10 and ~30 au is depleted of μm-size grains. We compare the J-, H-, and K-band spectra obtained with SINFONI in quiescence with the spectra taken during the outburst, showing that all the emission lines result from the episodic accretion event. Conclusions. Based on the morphology analysis, we favor the scenario that assumes the scattered light is coming from a circumstellar disk rather than the outflow around EX Lup. We determine the origin of the observed feature as either coming from a continuous circumstellar disk with a cavity, from the illuminated wall of the outer disk, or from a shadowed disk. Moreover, we discuss the potential origins of the depleted region of μm-size grains, exploring the possibility that a sub-stellar companion may be the source of this feature.
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Petrauskas, А. V., D. V. Bibikov, V. H. Ivakin, and S. V. Pavlenko. "THE ARTICLE DEDICATED TO THE RESEARCH OF THE MEDIEVAL MOUND NEAR THE VILLAGE TEPENYTSIA (to the Question of the Mounds with Stone Constructions at the Middle Dnieper Region)." Archaeology and Early History of Ukraine 30, no. 1 (March 25, 2019): 75–95. http://dx.doi.org/10.37445/adiu.2019.01.08.
Full textAbstract:
In the summer of 2015, Zhytomyr expedition conducted archaeological research at the burial mounds at the tract of Long Niva near the village Tepenitsa Olevsky district of Zhytomyr region. As a result, the burial with a stone construction under the embankment was explored and studied. The stone cover was discovered right after the turf layer and completely covered the embankment as if it was an armor. The construction consisted of granite fragments and pieces of quartzite and sandstone. At the bottom of the embankment were stone boulders of large size that became smaller at the top of burial. At the level of the mainland around the embankment placed small ditch that had a form of two arcuate sections. Remains of a skeleton or gravel pit in the burial mound was not discovered (cenotaph). Two large fragments of the potter’s pot was found on the sand pit in the central part of the embankment at the level of the ancient horizon. The practical absence of inventory does not allow date the archaeological complex clearly. A fragment of the pot can be attributed to two chronological periods: the end of IX — the first half of the X century or the second half of the XIII — XIV centuries.
The stone constructions in the burial mounds are not inherent for Old Russian time in Ukraine. Stone fixt only in slightly more than 1 % of all investigated burial mounds. The discovery of such rare complex forced the authors refer to the history of research of this type of monuments on the territory of Ukraine. In the Middle Dnieper area, burial mounds with stone structures are located in two regions: on the territory of Zhytomyr Polissya (Ubort river basin, Slovechansko-Ovruch ridge) and in Porossya.
The burial groups in Zhytomyr region were explored by the excavations of Ya. V. Yarotsky (1902), O. A. Fotinsky (1904), M. B. Shchukin (1976), B. A. Zvizdetsky (1988, 1996—1999), the exploration of V. O. Misiats (1961, 1978), A. P. Tomashevsky and S. V. Pavlenko (1996, 2006, 2013). There are 18 gravediggers with stone burial mounds on this territory currently. 42 burial mounds were excavated (more than 300 known). At the 29 burial complexes were fixed stones fragments. These sights don’t occupy a separate compact area and located next to burial mounds consisting exclusively of mounds with simple earthen embankments. Only at the 7 necropolises majority burial mounds contains stones. On other monuments such burial mounds was few. Different methods of using stones have been recorded in investigated burial mounds. Often different variants of stone designs are fixed in one monument. Different kinds of stone were used for constructions: sandstone, granite, quartzite. In burial mounds with stone structures under the embankment are fixed various types of burial ceremony (cremation on the site, cremation on the side, inhumation on the horizon, inhumation in undermount pits, cenotaph). The ritual is accompanied by typical Slavic equipment. The earliest complexes are dated by the X century, the most recent are the second half of the XIII century.
Stone barrows Porossya are known since the middle of the nineteenth century (about 500 individual complexes was fixet). They were discovered by V. B. Antonovych (70s of XIX century), T. M. Movchanivsky (1928), V. Ye. Kozlovskaya (30s of the XX century), R. S. Orlov and P. M. Pokas (1986, 1988). 9 burial mounds with stone constructs under the embankment are known on the territory of Porossya. 78 monuments have been investigated at 5 a monuments, 37 of them — with stone crepes (the structure was mostly fixed in the of circle form of boulders, which engird the embankment). The burial ceremony and accompanying equipment are typical for Slavic monuments.
There are two main hypotheses about the origin of this type of monuments. According to the first, the stone structures in the mounds are a purely practical tradition of local people, which arose in the territories characterized by significant presence of the stone (O. A. Fotinsky, V. B. Antonovych, A. V. Petrauskas). According to the second hypotheses, use of a stone is a tradition of the Slavic alien population. Ya. V. Yarotsky considered that this is a memorial of the Dregovichi burial mounds of Zhytomyr Polissya, Western Balts (Yotvingians) — I. P. Rusanova, B. A. Zvizdetsky, A. P. Tomashevsky, mixed Baltic-Dregoviches population — V. V. Sedov and A. P. Motsia. The tradition of using stones in the burial mounds of Porosyya was explained by the borrowing of the elements of the burial ceremony of the nomads S. V. Shamray, I. P. Rusanovа and O. P. Motsia. Influenced by the coming population from the western and northern territories of Old Rus — L. I. Ivanchenko. Some researchers have ruled out both hypotheses.
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Norman, David B. "Scelidosaurus harrisonii from the Early Jurassic of Dorset, England: the dermal skeleton." Zoological Journal of the Linnean Society 190, no. 1 (January 27, 2020): 1–53. http://dx.doi.org/10.1093/zoolinnean/zlz085.
Full textAbstract:
Abstract Cranial exostoses (areas of periosteal ornamentation) are present on the external surfaces of the skull and mandible of Scelidosaurus harrisonii. True osteoderms have also been identified on the skull, forming a ‘brow-ridge’ of three supraorbital bones, dished plates that are attached to the lateral surface of the postorbitals and a pair of larger, horn-shaped structures that project from the posterodorsal surface of the occiput. Postcranial osteoderms form an extensive series of oval-based, ridged osteoderms that extend backward across the dorsal and lateral surfaces of the neck and torso. Smaller, narrow-based ridged osteoderms are also found on the lateral surfaces of the limbs. The tail is surrounded by four longitudinal rows of large, narrow-based, ridged or keeled osteoderms. The neck, unlike the rest of the body, is encased dorsolaterally by a variety of osteoderms. These can be differentiated into two fundamental types: base-plate osteoderms that develop deep within the compact layers of the dermis and, superficial to each base-plate, tall, ridged or cap-like osteoderms. These latter, project outward from the skin surface and were covered by an epidermal scale or a rigid keratinous sheath. The base-plates are true osteodermal components, but to differentiate them from the more familiar superficial osteoderms, they will be called here simply ‘base-plates’. Lying on the dorsal midline between and beneath the occipital horns is a single, ridged, nuchal osteoderm comprising a base-plate and osteoderm cap. The nuchal plate is flanked by a pair of prominent ‘tricorn’ osteoderm arrays mounted on shallowly arched blocks of fused base-plate osteoderms. Behind the tricorn arrays is a succession of four partial collar-like arrays of osteoderms formed (at least in ontogenetically mature specimens) by coalesced base-plates that anchor tall and either carinate or more plate-like osteoderms. The largest of these are always positioned on the ventrolateral margin of each collar. The osteoderms become progressively smaller toward the midline. It is at present unclear whether the base-plate supported collar arrays on either side fuse together along the midline to form cervical half-rings, as is often reported in more derived ankylosaurian thyreophorans. Individual collar arrays do not imbricate with each other, but are likely to have been interconnected by sheets of tough connective tissue. On the ventrolateral flanks of the pectoral region are found the largest, bladed osteoderms. In two partly articulated skeletons an osteoderm is preserved on the posterodistal surface of the scapular blade. Although this position is reminiscent of the parascapular spines found in some stegosaurs, these bones are not regarded as homologues; their placement is a coincidence of positioning an osteoderm row adjacent to the scapular blade. The torso preserves three principal rows of large, ridged osteoderms that show no evidence of accompanying base-plates. The ventrolateral row has the largest osteoderms and these are succeeded in size by the lateral row and dorsolateral row, respectively. There is no evidence to support the existence of a midline dorsal row of osteoderms. The principal rows extend backward across the dorsal and lateral flanks of the body as far as the pelvic area. Smaller cap-shaped osteoderms are scattered between the principal rows, but whether they were organized into subsidiary rows or were more randomly distributed cannot be ascertained. Smaller, narrow-based, ridged osteoderms are found in oblique rows across the anterior chest; they also flank the proximal half of the forelimb (as far as the elbow) and extend to the ankle region in the hind limb. The tail is surrounded by large, narrow-based, high-ridged osteoderms. Unlike the neck and torso, there is a row of dorsal midline osteoderms that are flanked by large, lateral osteoderms, and beneath these there is a midline ventral row. The latter are close-set and particularly deeply keeled in the area nearest to the pelvis. Osteoderms vary considerably both in structure and texture. Base-plates have a rough, porous external texture as a consequence of the abundant vascular canals that penetrate these bones. Internally, their surface is arched and has a woven-textured fabric comprising bundles of mineralized fibres interspersed with large vascular foramina. Accompanying osteoderms are generally a little denser than their base-plates and have a smoother cortex, although abundant small foramina and shallow vascular channels pit and groove this external surface. The pair of occipital osteoderms closely resemble bovid (ungulate mammal) horn-cores and are likely to have been sheathed by keratin (as preserved exceptionally in the ankylosaurians Zuul and Borealopelta). Farther posteriorly, the principal osteoderms in the major rows along the torso and tail are generally thin-walled, cap-shaped and ridged. They have a rough and porous external surface, which suggests that the bone surface was covered by keratinous scales. The generally porous fabric of these osteoderms has been remarked upon and it is probable that these were flushed with blood. Interspersed between the visually dominant parasagittal rows of osteoderms is a scattering of smaller cap-shaped osteoderms and polygonal or rounded, flat ossicles. Scattered populations of these ossicles were probably lost because they were, in effect, ‘invisible’ during excavation and skeletal preparation, being of millimetric dimensions. These smaller osteodermal ossicles formed a mosaic-like pattern on the skin surface and toughened the flexible portions of the skin of the animal. Skin impressions and epidermal peels, probably deriving from the ventral surface of the body, reveal a closely packed mosaic of smaller flat osteoderms that underlie similarly shaped keratinous scales. The discovery of smaller, partly articulated skeletons has revealed aspects of the growth and development of the cervical osteoderm arrays. Individual base-plates begin to form deep in the dermis through mineralization of the woven connective tissue fibres in the stratum compactum and, as these thicken, they also involve the looser and more irregular fibres of the stratum superficiale. Individual base-plates expand peripherally, deepen and form shallowly convex pads externally upon which primordial osteoderms developed. The latter form initially as narrow, elongate, pup-tent-shaped structures with a posteriorly off-set apex and arched, slightly hollow bases. Differential patterns of mineral deposition progressively modify these ‘templates’ into the range of osteoderm morphologies seen in ontogenetically mature skeletons: from subconical curved horns, through tall, carinate blades, to extremely tall, plate-shaped structures, as well as to the simpler oval-based, ridged, pup-tent-shaped osteoderms. As the skeleton approaches full size, in the neck region the base-plates and their osteodermal caps fuse together, and adjacent base-plates interlock before finally fusing together to form partial collars that anchor and support transverse arrays of prominent osteoderms. Osteoderms had the potential to contribute to a number of biological roles in the life of these animals, including protection (defence-retaliation), thermoregulation and more subtle aspects of their behaviour.
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Motušić, Eugen. "Porušena crkva Rođenja Blažene Djevice Marije u Silbi." Ars Adriatica, no. 4 (January 1, 2014): 347. http://dx.doi.org/10.15291/ars.508.
Full textAbstract:
It is known that the Church of the Nativity of the Blessed Virgin Mary at Silba was demolished in 1828 so as to provide the necessary building material for the completion of the new parish church which inherited the dedication from the old one. As we learn from the archival records, the demolition was authorized by the Archbishop of Zadar Josip Nowak who stipulated that the Franciscan Church of Our Lady of Carmel would function as the local parish church while the new one was being built. All that remains from the old church today is the bell tower which continued to be used by the new parish church. It is obvious from the schematic ground plan and the dimensions of the demolished church, recorded in the now lost document from the parish church archive, that it was a single-nave longitudinal structure with a rectangular sacristy to the east, two shallow chapels extending from the lateral walls and a porch of the lopica type (resembling a loggia) at the front which abutted onto the corner of the bell tower with its own south corner. Apart from the high altar, placed against the back wall, the church had three pairs of side altars. The analysis of the canonical visitations carried out during the second quarter of the seventeenth century demonstrates that the church, recorded for the first time in 1579, was a modest building in which the oil for the anointment of the sick was being kept because the local parish church of that time, dedicated to St Mark, was too far from the village. The church was provided with five side altars put up by the more distinguished individuals and members of the lay fraternities the most prominent of which was that of Our Lady of the Rosary after which the church was called by eighteenth-century locals. Based on the analysis of the 1670 visitation of Archbishop Evangelisto Parzaghi who described the renovation during which certain altars changed their places, the article argues that the church was completed just before this visit. The bell tower was mentioned as a campanile for the first time in 1678.By means of comparative analysis, it can be established that the Church of the Nativity of the Virgin at Silba belonged to the same architectural type as a large group of simple yet spacious churches which were built in rural communities along the east Adriatic coast by local masters during the seventeenth and eighteenth centuries. The activity of such masters on the island of Silba is corroborated by contemporary birth, marriage and death records as well as a number of monuments such as a tombstone in the Church of St Mark and the door lintel in the house of master builder Franić Lorencin (1660), both of which depict building and carving tools. The analysis of the land registry maps and topographical drawings of 1824 and 1833 shows that the church’s south wall, to the east of the chapel of Our Lady of the Rosary, was laid in a different direction compared to that of the rest of the wall, indicating that this portion belonged to an earlier layer of the building which, judging from everything, seems to have been medieval. Therefore, the wall was widened and extended towards the west during the rebuilding documented in the visitation of 1670. This possibility, which a future excavation of the site ought to be confirm, is strengthened by the frequency of such alterations as can be seen on the seventeenth- and eighteenth-century churches on the island of Ugljan and in particular on the Church of St Lawrence at Lukoran, built in 1632, which is the best example of that architectural type.Another feature of these churches is the lopica-type porch which stands out as an architectural element typical of Istria and the Quarnero gulf to which, geographically speaking, the island of Silba gravitates. The lopica porch of the Church of the Nativity at Silba had a particularly elongated plan and featured two symmetrical sets of three supports and an axial main entrance into the porch, that is, the church. It is unlikely that the porch was added prior to the late seventeenth century because during that time, Silba was exposed to the raids of the Turkish pirates who threatened it directly. It is certain that the bell tower was used for defensive purposes and the addition of a porch would have diminished its importance as a fortification structure and hampered the visual communication with the entrance to the church.The examination of the architecture of the bell tower revealed two different building phases: an earlier one which included the body of the bell tower and a later one which saw the addition of the pyramidal structure together with a shallow square drum. In its original form, the bell tower had a compact body featuring a round-headed opening at the centre of each side of the two topmost storeys. Their stylistically undefined morphology corresponds to modest bell towers which were built in this area from the late sixteenth to the eighteenth century. The original pyramidal top had to be dismantled in 1858 due to wear and tear and it was replaced by the present one which has oval openings at the bottom of each side of the drum. This structure is almost identical to the top of the bell tower of the Church of Our Lady of the Rosary at Preko on the island of Ugljan which was built in 1844.Based on the archival records, the article also establishes that the substantially repainted image of the Virgin and Child with SS Mark and Matthew, today at the high altar of the parish church, was originally larger. It was the object of ex-voto veneration and numerous offerings had been placed in its glass case. The painting was cropped so that it could be inserted into the niche of the marble altar piece designed by Ćiril M. Iveković (1898) which meant the loss of the two evangelists. According to the preserved contract and drawing, the lower part of the altar was set up in 1860 by Giovanni dalla Zonca, an altar maker from Vodnjan, and it featured the still preserved wooden statues of SS Peter and Paul which are dated to the mid-seventeenth century on the basis of their stylistic features. Therefore, it can be concluded that painting and the statues were taken from the high altar of the demolished church.
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Vukovic, Jasna. "Pottery shreds as tools in late Neolithic Vinca." Starinar, no. 63 (2013): 191–207. http://dx.doi.org/10.2298/sta1363191v.
Full textAbstract:
Over the last few years, careful analysis of a large quantity of ceramic material found during excavation at Vinca has identified a significant number of ceramic fragments with clear use-wear traces. Recycled fragments of ceramic vessels are characterized by the presence of damage and deformation caused by abrasive processes i.e. contact of the fragments with hard material. All recorded recycled fragments can generally be divided into two basic groups: fragments representing tools with a working edge, and fragments with traces of abrasion on their outer surface. The largest group comprises fragments whose edges form the working edge of a tool, rounded or flattened through use and so becoming smooth. In contrast to so-called burnishers (the secondarily used, striped handles with traces of the action of water, manifesting in a uniformly rounded break) with ceramic tools only one edge of the fragment is rounded and used; the remaining edge indicates a completely normal break. In addition, most fragments also have abrasions directly beneath the working edge, which indicates holding the tool at a certain angle during use. That damage can occur both on the exterior and interior surfaces. It is striking that in a large group of fragments, the rim is used as a working edge. Tools are mostly fragmented, but it appears that their shape was not modified before use. In that sense, two straight polygonal tools can be distinguished (T. I/1a-b), or tools which are rectangular in shape with rounded corners (T. II4a-b), preserved complete. In most cases, these are fragments of bowls, so tools usually have polished or burnished surfaces, but ornamental parts formed by burnished lines or channelling are also noticeable. Fragments of rough fabric were never used as tools, but only those with an admixture of fine sand. Very rarely, actually in two cases, fragments of amphorae were used as tools (T. IV/2,5). Usually the upper parts of vessels were used, although there are several exceptions, where parts of the base and body were used as well (T. IV/3). Also, in the damaged area straight depressions can often be noticed, which apparently represent some kind of negative impression of the object on which they were used, or, in rare cases, the whole working surface is step-like. The second group of fragments do not generally differ from the first group as regards their form and the surface treatment. The difference can be seen in the distribution of damage. To be precise, the zone of intensive abrasion lies on the surface of fragments and is manifested by complete removal of original surface, while across it, marks caused by contact with hard material often result in deep incisions, which can be seen with the naked eye. These marks can be found on the most protruted parts of vessels i.e. on the shoulder, apart from two cases concerning the shoulder, or the thickened rim of an amphora (T.V/1,5). Finally, we should emphasise the fact that not one ceramic tool has been found around an architectural structure. Specimens originate from archaeological layers or contexts which do not represent a specific zone of activity (destruction layers, ditch filling, posthole, levelling layers etc) but in contexts in which waste material was deposited. From that perspective, one example can particularly be distinguished, a tool with a working edge found near the ceramic substructure of a oven. By analysis of the distribution, shape and kind of damage, as well as the position and shape of the working edge, it is possible to reconstruct the direction of movement and position of the tool during use. Scraping tools show marks in the form of dense incisions, visible both macroscopically and microscopically. They can also be characterised by a pronouncedly rounded working edge. Bearing these characteristics in mind, tools from Vinca with rounded working edges can be categorized as tools for scraping away excess clay and for thinning the surface of unfired vessels. They were held at right angles or slanting in relation to the vessel, with the working edge horizontal or also at an angle or lateral to the working edge, so that the vessels walls were thinned by movements in various directions. Ceramic tools were not specialized, and were undoubtedly multi-functional. They could have been used for smoothing and polishing. This is supported by the fact that abrasion traces are parallel or distributed in various directions. A group of tools with a flattened working edge, judging by preserved marks, had a rather different function. There are indications that these were held at right angles to the vessel but that the movement was not lateral. The tool was probably held with the working edge in a vertical position, so that burnished decoration could be carried out by using up/down movements, when it was necessary to make thin burnished lines of uniform thickness and with clearly defined edges. Bearing in mind traces of 'negative' impressions of the item on which the tools were used, the tool could also have been used in a left-right direction, when it was used to execute the burnished zone typical for upper bowls' parts. One of the important characteristics of ceramic tools is the use of the rim of a broken vessel as a working edge. This is a very logical choice. Bowl rims have a naturally rounded and often symmetrical, sharpened shape. Thus, craftsmen got a ready-made thin, relatively sharp tool, so there was no need to modify a fragment or re-shape it for the working edge to obtain the desired shape. Likewise, as mentioned before, the existence of a negative impression on work edges, usually rims, makes it probable that such tools were used to shape and burnish the rims of vessels. It is an interesting fact that most of these tools comprise fragments of bowls, and this is not coincidental. Important role in the appearance and form of traces caused by abrasive processes is played by characteristics of the abrasive, i.e. tool, such as hardness and granulation. All bowls are characterised by their fine fabric and fine-sand admixture, thin walls, burnished or polished surfaces and firing in a reduced atmosphere. These characteristics are very significant regarding the reaction of material to mechanical stress. A reduced atmosphere during firing increases the hardness of ceramics. Ceramics with fine granulation and lower porosity show greater resistance to mechanical stress than ceramics of rougher fabric with larger quantities of a coarse admixture. Burnishing and polishing lead to the compression of particles on surfaces, which creates a hard, compact structure, resistant to abrasion. It was especially convenient to have tools made of materials with identical characteristics as material they were used on. Analysis of ceramic fragments from the early phase of the Late Neolithic settlement at Vinca indicated an exceptional number of recycled vessel fragments, shaped as tools and used in the process of shaping and modifying ceramic surfaces. Since this concerns a new class of archaeological finds, it is necessary to suggest a direction for future research, particularly experimental, which would, together with microscopic identification of use-wear traces, reveal completely the activities in which ceramic tools were used.
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"Versatile new Liebherr R 924 Compact Tunnel short-tail excavator / . ENeuer Liebherr-Kurzheckbagger R 924 Compact Tunnel für flexible Einsätze." Geomechanics and Tunnelling 3, no. 3 (June 2010): 327–28. http://dx.doi.org/10.1002/geot.201090021.
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Tokar, Nikolai, Zelgedin Mevlidinov, Tatiana Levkovich, and Alexandr Foevtsov. "Scientific and organizational support for implementation of the strategy of innovative development of production in road construction complex with application of automobraders with additional universal working equipment." Russian journal of transport engineering 6, no. 2 (June 2019). http://dx.doi.org/10.15862/06sats219.
Full textAbstract:
The work outlines ways to intensify the production of planning and loading and unloading operations in a road-building complex using motor graders with controlled excavator equipment using comparative, logical analysis and synthesis. The study of the representativeness and technical condition of car parks, as well as indicators of their application revealed the following: the structure of machine parks contains a narrow range of nomenclature and the machines of small and medium sizes prevail; in the structure of the machine parks, the outdated planning and earthmoving machinery are represented – 52,7 %; loaders from 5,1 % to 10,5 %; hand mechanized tools – 17 %; equipment with high physical deterioration is more than 60 %; equipment leased from third-party organizations on a permanent basis is 17 %, and the total amount leased is 1,5 %. The main idea of the new approach is the idea of forming a compact fleet of vehicles in order to reduce the cost of maintaining it by incorporating universal equipment into the composition, each unit of which can perform the functions of 2–4 machines with the complete elimination of works on re-equipment of replaceable working bodies. In the course of research, additional working equipment of a motor grader was proposed, located in front of the machine, is a loader’s working equipment consisting of a bucket, boom, thrust, hydraulic bucket and boom control cylinder, in the upper part of the rear wall of the bucket, rigidly mounted excavator equipment, represented by two brackets driven by a hydraulic motor. Inside the brackets by means of a swivel is fixed an arrow with a handle, in the coupling of which there is a hydraulic motor, which is connected to the bucket. Lifting and lowering excavator equipment is performed by two hydraulic cylinders, hinged to the brackets and the boom. Forecast calculations showed that the cost of a modular multifunctional motor grader will on average be about 4 million rubles. The volume of capital investments for the purchase of a compact fleet of vehicles for an average enterprise of a road-building complex in the urban economy based on the use of multi-functional modular equipment will amount to approximately 24 million rubles. The payback period is 2–2,5 years. As a result of the research, the composition and structure were determined, the main ways of intensifying the planning and loading and unloading operations in the road-building complex with the use of motor graders with controlled excavator equipment were proposed.
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"The influence of mechanical conditions on the healing of experimental fractures in the rabbit: a microscopical study." Philosophical Transactions of the Royal Society of London. B, Biological Sciences 313, no. 1161 (September 24, 1986): 271–302. http://dx.doi.org/10.1098/rstb.1986.0038.
Full textAbstract:
To examine in detail the events that lead to healing under different mechanical conditions, experimental fractures of the rabbit tibia were immobilized with either a metal compression plate or a plastic plate, to produce stable or unstable mechanical conditions respectively. To fracture the bone, a small saw cut is made in the medial cortex and three-point pressure is then applied to fracture the remaining cortical bone. A small amount of bone is removed by the saw cut. This is of no consequence when a plastic plate is used because the plate is designed so that a small gap remains between the fractured surfaces. When a compression plate is used, a gap approximately 100 pm wide remains under the plate. In addition, despite the use of compression, only part of the fractured surfaces are normally in contact, so other narrow fracture gaps may remain. The fractures were examined at experimental times from 4 days to 1 year by both light and electron microscopy. In stable mechanical conditions, a thin layer of periosteal callus starts to form within 4 days and healthy mesenchymal cells and capillaries are adjacent to the fracture. By 7 days the callus is fully developed and is covered by a new periosteum. Over the following weeks it becomes more compact as the cavities are filled by bone. The endosteal callus, if formed, is small. From 9 days onwards the fracture gaps of between 30 and 100 pm are invaded by mesenchymal cells; macrophages remove the debris and fibroblasts lay down a collagenous matrix. Capillaries are numerous. By 2 weeks, these gaps are lined by osteoblasts producing transverse layers of new bone on the fractured surfaces. The gap is rapidly filled by transversely orientated bone to achieve union by 3-4 weeks. Resorption is limited to very small, isolated regions of the fractured surfaces. The gaps between 10 and 30 μm wide appear to be too narrow for cells and capillaries to enter, and they are widened by osteoclastic action. Mesenchymal cells and capillaries then enter and bone is laid down on the surfaces of the newly excavated cavities. After union, the region is recognized as a wide band of irregularly organized bone. In compressed regions, areas of actual contact are very few, and narrow gaps can be seen. Union is achieved by direct Haversian remodelling across gaps up to 9 pm wide. Remodelling starts at about 3 weeks and it is part of the normal process that occurs after union of a fractured cortex. The events in the fractures healing under unstable mechanical conditions diverge immediately. The initial periosteal reaction is similar, but cancellous bone forms only away from the fracture gap. Mesenchymal cells in a fibrous matrix, but with very few, if any, associated capillaries, persist as a thick layer over the fracture gap. At 6 days islands of cartilage begin to develop, and by 12 days the whole central area is filled by a cartilaginous matrix containing thick and thin collagen fibrils and elastic fibres. The cartilage is replaced by bone by 3-4 weeks. At this point, healthy cells and capillaries are found near the fracture gap. A small endosteal callus may form in a similar way. The fracture gaps are now invaded. The debris is removed by macrophages, and fibroblasts produce a collagenous matrix. Osteoclasts cover the fractured surfaces, but the amount of resorption is minimal. Capillaries also enter the gap. Within 1-2 weeks the gap is filled by transverse lamellae of bone. Once the fractured cortex is united, the events are similar in both series of fractures. Resorption of any callus starts. In the periosteal callus, large cavities form particularly along the callus-cortex junction. Over the next 3 months the callus is resorbed and the cortex is extensively remodelled. By 18 weeks no callus remains. The cortical bone is compact, but large cavities filled with fat cells may occur. The overall dimensions of the bone may be larger than that of the contralateral normal tibia, but the layer of cortical bone is thinner. Thus the plate, whether of metal or plastic, affects the structure of the bone. This study serves to emphasize that the mechanical stability of a healing fracture determines the composition and size of the periosteal callus and the time at which union across a fracture gap is achieved. The fracture fragments must be mechanically stable, so that there is no movement at the fracture gap before cells can enter and lay down new bone. This may be achieved immediately, though artificially, by a metal compression plate, or slowly, though naturally, by the formation of a large callus of cancellous bone. The movements and differentiation of the cells involved in healing are discussed. This experimental fracture model will form a basis for future experimental studies of healing fractures.