scholarly journals Study on Temperature Control and Crack Prevention of Mass Concrete for Large Powerhouse Constructed in Cold Area

2019 ◽  
Vol 275 ◽  
pp. 02009
Author(s):  
Qiaorong Sun ◽  
Bingyong Ding ◽  
Zaixin Zheng ◽  
Running Du ◽  
Sheng Qiang
Keyword(s):  
Temperature Control ◽  
Large Scale ◽  
Complex Structure ◽  
Cold Climate ◽  
Hydropower Station ◽  
Mass Concrete ◽  
Unusual Structure ◽  
Finite Element Program ◽  
Cold Area ◽  
Multiple Materials

Due to complex structure, large scale, and cold climate, the temperature field and stress field during construction of BoYi Station is different with ordinary mass concrete. Therefore the corresponding crack prevention method must be explored. In order to simulate the complicated construction course, cold climate, multiple materials and unusual structure, a finite element program is adopted. In 5 numerical simulation cases, different temperature control methods are tried to decrease the tensile stress of mass concrete. Based on the simulation analysis and combined with the engineering experience, the scheme and indexes of temperature control and crack prevention are recommended. The mainly measures are controlling pouring temperature, insulation of concrete surface, pipe cooling, block partition and extra steel bar reinforcement. The values of temperature indexes are sharply lower than that of ordinary hydropower station mass concrete. The suggested measures and indexes in this paper, which are various with season, structure position and material, may provide some reference to similar large hydropower station workshop in cold area.

scholarly journals Performance of Strawberry Varieties Developed for Perennial Matted-Row Production in Annual Plasticulture in a Cold Climate Region

Agronomy ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1407
Author(s):  
Courtney A. Weber
Keyword(s):  
Large Scale ◽  
Fruit Size ◽  
Weather Conditions ◽  
Cold Climate ◽  
Annual Production ◽  
High Yield ◽  
Production Cycle ◽  
Late Season ◽  
Berry Weight ◽  
High Yields

Annual plasticulture production of strawberries promises superior weed control, fruit quality and yields. However, strawberry varieties adapted for perennial, matted-row production and local markets in cold climate regions have not been widely tested for adaptation to an annual production cycle. Productivity of seven short-day varieties developed for matted-row and/or annual production was examined in an annual plasticulture system in two consecutive trials in central NY (lat. 42.87° N, long. 76.99° W) harvested in 2013 and 2014. ‘Flavorfest’ demonstrated good performance in Trial 1 with high yield (390 g/plant) and large fruit size (13.9 g mean berry weight). ‘Jewel’ was shown to be well adapted to the annual plasticulture system with consistently high yields (330 and 390 g/plant) that equaled or surpassed other varieties and had moderate fruit size. ‘Chandler’ performed similarly to previous trials conducted in warmer regions with yield (340 g/plant) and fruit size (9.8 g mean berry weight) similar to ‘Jewel’. ‘Clancy’ yielded less but was consistent from year to year. The late season varieties Seneca and Ovation showed marked variability between years, possibly due to drastically different temperatures during flowering and fruit development in Trial 1 compared to Trial 2. High temperatures in Trial 1 likely caused higher early fruit yield, a compressed season and a precipitous decline in fruit size in the later season, thus reducing yield in the late season. Survival after a second dormant period was poor resulting in a small second harvest and reduced fruit size. Overall, the system demonstrated many of the expected benefits but may be more sensitive to weather conditions in the region. While many varieties developed for matted-row production may work well in an annual plasticulture system, not all varieties are equally adapted. Performance of each variety should be determined independently before large scale adoption by growers.

Health monitoring sensor placement optimization based on initial sensor layout using improved partheno-genetic algorithm

2020 ◽  
pp. 136943322094719
Author(s):  
Xianrong Qin ◽  
Pengming Zhan ◽  
Chuanqiang Yu ◽  
Qing Zhang ◽  
Yuantao Sun
Keyword(s):  
Genetic Algorithm ◽  
Health Monitoring ◽  
Large Scale ◽  
Complex Structure ◽  
Sensor Placement ◽  
Placement Problem ◽  
Optimal Sensor Placement ◽  
Placement Optimization ◽  
Sensor Placement Optimization ◽  
Sensor Locations

Optimal sensor placement is an important component of a reliability structural health monitoring system for a large-scale complex structure. However, the current research mainly focuses on optimizing sensor placement problem for structures without any initial sensor layout. In some cases, the experienced engineers will first determine the key position of whole structure must place sensors, that is, initial sensor layout. Moreover, current genetic algorithm or partheno-genetic algorithm will change the position of the initial sensor locations in the iterative process, so it is unadaptable for optimal sensor placement problem based on initial sensor layout. In this article, an optimal sensor placement method based on initial sensor layout using improved partheno-genetic algorithm is proposed. First, some improved genetic operations of partheno-genetic algorithm for sensor placement optimization with initial sensor layout are presented, such as segmented swap, reverse and insert operator to avoid the change of initial sensor locations. Then, the objective function for optimal sensor placement problem is presented based on modal assurance criterion, modal energy criterion, and sensor placement cost. At last, the effectiveness and reliability of the proposed method are validated by a numerical example of a quayside container crane. Furthermore, the sensor placement result with the proposed method is better than that with effective independence method without initial sensor layout and the traditional partheno-genetic algorithm.

Temperature Control and Anti-Cracking Measures for a High-Performance Concrete Aqueduct

2013 ◽  
Vol 405-408 ◽  
pp. 2739-2742 ◽  
Author(s):  
Zhen Hong Wang ◽  
Shu Ping Yu ◽  
Yi Liu
Keyword(s):  
Temperature Control ◽  
Temperature Difference ◽  
High Performance ◽  
High Performance Concrete ◽  
Concrete Structures ◽  
Apparent Temperature ◽  
Mass Concrete ◽  
Water Pipe ◽  
Thin Walled ◽  
Water Pipe Cooling

To solve the problem of cracks developing on thin-walled concrete structures during construction, the authors expound on the causes of cracks and the crack mechanism. The difference between external and internal temperatures, basic temperature difference and constraints are the main reasons of crack development on thin-walled concrete structures. Measures such as optimizing concrete mixing ratio, improving construction technology, and reducing temperature difference can prevent thin-walled concrete structures from cracking. Moreover, water-pipe cooling technology commonly used in mass concrete can be applied to thin-walled concrete structures to reduce temperature difference. This method is undoubtedly a breakthrough in anti-cracking technology for thin-walled concrete structures, particularly for thin-walled high-performance concrete structures. In addition, a three-dimensional finite element method is adopted to simulate the calculation of temperature control and anti-cracking effects f. Results show the apparent temperature controlling effect of water-pipe cooling for thin-walled concrete structures.

A new method for hydraulic mass concrete temperature control: Design and experiment

2021 ◽  
Vol 302 ◽  
pp. 124167
Author(s):  
Xiaochun Lu ◽  
Bofu Chen ◽  
Bin Tian ◽  
Yangbo Li ◽  
Congcong Lv ◽  
...  
Keyword(s):  
Temperature Control ◽  
Control Design ◽  
New Method ◽  
Mass Concrete ◽  
Concrete Temperature

scholarly journals Temperature Control to Improve Performance of Hempcrete-Phase Change Material Wall Assemblies in a Cold Climate

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5343
Author(s):  
Miroslava Kavgic ◽  
Yaser Abdellatef
Keyword(s):  
Phase Change ◽  
Phase Change Material ◽  
Temperature Control ◽  
Energy Demand ◽  
Control Strategies ◽  
Cold Climate ◽  
Embodied Energy ◽  
Energy Storage Materials ◽  
Hysteresis Phenomenon ◽  
Change Material

Phase change material (PCM)-enhanced building envelopes can control indoor temperatures and save energy. However, PCM needs to undergo a phase change transition from solid to liquid and back to be fully effective. Furthermore, most previous research integrated PCM with high embodied energy materials. This study aims to advance the existing research on integrating PCM into carbon-negative wall assemblies composed of hempcrete and applying temperature control strategies to improve wall systems’ performance while considering the hysteresis phenomenon. Four hempcrete and hempcrete-PCM (HPCM) wall design configurations were simulated and compared under different control strategies designed to reduce energy demand while enhancing the phase change transition of the microencapsulated PCM. The HPCM wall types outperformed the hempcrete wall assembly through heating (~3–7%) and cooling (~7.8–20.7%) energy savings. HPCM walls also maintained higher wall surface temperatures during the coldest days, lower during the warmest days, and within a tighter range than hempcrete assembly, thus improving the thermal comfort. However, the results also show that the optimal performance of thermal energy storage materials requires temperature controls that facilitate their charge and discharge. Hence, applied control strategies reduced heating and cooling energy demand in the range of ~4.4–21.5% and ~14.5–55%, respectively.

scholarly journals A climatic thermostat making Earth habitable

2005 ◽  
Vol 4 (1) ◽  
pp. 3-7 ◽  
Author(s):  
Peter D. Ditlevsen
Keyword(s):  
Surface Temperature ◽  
Temperature Control ◽  
Black Body ◽  
Black Body Radiation ◽  
Cold Climate ◽  
Snowball Earth ◽  
Greenhouse Warming ◽  
Radiative Balance ◽  
The Mean ◽  
Warm State

The mean surface temperature on Earth and other planets with atmospheres is determined by the radiative balance between the non-reflected incoming solar radiation and the outgoing long-wave black-body radiation from the atmosphere. The surface temperature is higher than the black-body temperature due to the greenhouse warming. Balancing the ice-albedo cooling and the greenhouse warming gives rise to two stable climate states. A cold climate state with a completely ice-covered planet, called Snowball Earth, and a warm state similar to our present climate where greenhouse warming prevents the total glaciation. The warm state has dominated Earth in most of its geological history despite a 30% fainter young Sun. The warming could have been controlled by a greenhouse thermostat operating by the temperature control of the weathering process depleting CO2 from the atmosphere. This temperature control has permitted life to evolve as early as the end of the heavy bombardment 4 billion years ago.

Ultrasonic Nondestructive Testing for In-Line Monitoring of Wire-Arc Additive Manufacturing (WAAM)

2020 ◽  
Author(s):  
Md Shahjahan Hossain ◽  
Hossein Taheri ◽  
Niraj Pudasaini ◽  
Alexander Reichenbach ◽  
Bishal Silwal
Keyword(s):  
Quality Assurance ◽  
Additive Manufacturing ◽  
Nondestructive Testing ◽  
Large Scale ◽  
Gas Flow ◽  
Complex Structure ◽  
Process Condition ◽  
Process Conditions ◽  
Ultrasonic Signals ◽  
Wire Arc Additive Manufacturing

Abstract The applications for metal additive manufacturing (AM) are expanding. Powder-bed, powder-fed, and wire-fed AM are the different kinds of AM technologies based on the feeding material. Wire-Arc AM (WAAM) is a wire-fed technique that has the potential to fabricate large-scale three-dimensional objects. In WAAM, a metallic wire is continuously fed to the deposition location and is melted by an arc-welding power source. As the applications for WAAM expands, the quality assurance of the parts becomes a major concern. Nondestructive testing (NDT) of AM parts is necessary for quality assurance and inspection of these materials. The conventional method of inspection is to perform testing on the finished parts. There are several limitations encountered when using conventional methods of NDT for as-built AM parts due to surface conditions and complex structure. In-situ process monitoring based on the ultrasound technology is proposed for WAAM material inspection during the manufacturing process. Ultrasonic inline monitoring techniques have the advantages of providing valuable information about the process and parts quality. Ultrasonic technique was used to detect the process condition deviations from the normal. A fixture developed by the authors holds an ultrasonic sensor under the build platform and aligned with the center of the base plate. Ultrasonic signals were measured for different process conditions by varying the current and gas flow rate. Features (indicators) from the radio frequency (RF) signal were used to evaluate the difference in signal clusters to identify and classify different build conditions. Results show that the indicator values of the ultrasonic signals in the region of interest (ROI) changes with different process conditions and can be used to classify them.

Oceanography of the New Zealand subantarctic region

2021 ◽  
Author(s):  
◽  
Aitana Forcén-Vázquez
Keyword(s):  
New Zealand ◽  
Interannual Variability ◽  
Water Column ◽  
Large Scale ◽  
Southern Oscillation ◽  
Complex Structure ◽  
Positive Trend ◽  
Intermediate Water ◽  
Subantarctic Region

<p>Subantarctic New Zealand is an oceanographycally dynamic region with the Subtropical Front (STF) to the north and the Subantarctic Front (SAF) to the south. This thesis investigates the ocean structure of the Campbell Plateau and the surrounding New Zealand subantarctic, including the spatial, seasonal, interannual and longer term variability over the ocean properties, and their connection to atmospheric variability using a combination of in-situ oceanographic measurements and remote sensing data.  The spatial and seasonal oceanographic structure in the New Zealand subantarctic region was investigated by analysing ten high resolution Conductivity Temperature and Depth (CTD) datasets, sampled during oceanographic cruises from May 1998 to February 2013. Position of fronts, water mass structure and changes over the seasons show a complex structure around the Campbell Plateau combining the influence of subtropical and subantarctic waters.  The spatial and interannual variability on the Campbell Plateau was described by analysing approximately 70 low resolution CTD profiles collected each year in December between 2002 and 2009. Conservative temperature and absolute salinity profiles reveal high variability in the upper 200m of the water column and a homogeneous water column from 200 to 600m depth. Temperature variability of about 0.7 °C, on occasions between consecutive years, is observed down to 900m depth. The presence of Subantarctic Mode Water (SAMW) on the Campbell Plateau is confirmed and Antarctic Intermediate Water (AAIW) reported for the first time in the deeper regions around the edges of the plateau.  Long-term trends and variability over the Campbell Plateau were investigated by analysing satellite derived Sea Level Anomalies (SLA) and Sea Surface Temperature (SST) time series. Links to large scale atmospheric processes are also explored through correlation with the Southern Oscillation Index (SOI) and Southern Annular Mode (SAM). SST shows a strong seasonality and interannual variability which is linked to local winds, but no significant trend is found. The SLA over the Campbell Plateau has increased at a rate of 5.2 cm decade⁻¹ in the last two decades. The strong positive trend in SLA appears to be a combination of the response of the ocean to wind stress curl (Ekman pumping), thermal expansion and ocean mass redistribution via advection amongst others.  These results suggest that the variability on the Campbell Plateau is influenced by the interaction of the STF and the SAF. The STF influence reaches the limit of the SAF over the western Campbell Plateau and the SAF influence extends all around the plateau. Results also suggest different connections between the plateau with the surrounding oceans, e.g., along the northern edge with the Bounty Trough and via the southwest edge with the SAF. A significant correlation with SOI and little correlation with SAM suggest a stronger response to tropically driven processes in the long-term variability on the Campbell Plateau.  The results of this thesis provide a new definitive assessment of the circulation, water masses and variability of the Campbell Plateau on mean, annual, and interannual time scales which will support research in other disciplines such as palaeoceanography, fisheries management and climate.</p>

Forming Canonical 8D Data Clouds to Explore the Transient Dynamics of Physical Stiffened Plates: A Machine Learning Approach for Complex Mechanical Structures

2020 ◽  
Author(s):  
Ioannis T. Georgiou
Keyword(s):  
Machine Learning ◽  
Large Scale ◽  
Complex Structure ◽  
Spatial Dimension ◽  
Physical Structure ◽  
Transient Dynamics ◽  
Alloy Plate ◽  
Considerable Uncertainty ◽  
Acceleration Signal ◽  
The Impact

Abstract This work presents a data-driven explorative study of the physics of the dynamics of a physical structure of complicated geometry. The geometric complexity of the physical system renders the typical single sensor acceleration signal quite complicated for a physics interpretation. We need the spatial dimension to resolve the single sensory signal over its entire time horizon. Thus we are introducing the spatial dimension by the canonical eight-dimensional data cloud (Canonical 8D-Data Cloud) concept to build methods to explore the impact-induced free dynamics of physical complex mechanical structures. The complex structure in this study is a large scale aluminum alloy plate stiffened by a frame made of T-section beams. The Canonical 8D-Data Cloud is identified with the simultaneous acceleration measurements by eight piezoelectric sensors equally spaced and attached on the periphery of a circular material curve drawn on the uniform surface of the stiffened plate. The Data Cloud approach leads to a systematic exploration-discovery-quantification of uncertainty in this physical complex structure. It is found that considerable uncertainty is stemming from the sensitivity of transient dynamics on the parameters of space-time localized force pulses, the latter being used as a means to diagnose the presence of structural anomalies. The Data Cloud approach leads to aspects of machine learning such as reduced dynamics analytics of big sensory data by means of heavenly machine-assisted computations to carry out the unparalleled data reduction analysis enabled by the Advanced Proper Orthogonal Decomposition Transform. Emphasized is the connection between the characteristic geometric features of high-dimensional datasets as a whole, the Data Cloud, and the modal physics of the dynamics.

Cracking and Temperature Control in Mass Concrete Construction

2012 ◽  
Vol 446-449 ◽  
pp. 841-845
Author(s):  
Zhong Qing Xu ◽  
Yong Gang Ding ◽  
Chang Yi Zhai ◽  
Qiang Jun Li
Keyword(s):  
Temperature Control ◽  
Mass Concrete ◽  
Concrete Construction
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