Half Scale Research Articles

Realized normal volatility and maximum outlying jumps in high frequency returns for Korean won–US Dollar

This paper analyzes the realized volatility and jumps of five-minute returns for the Korean won–US dollar exchange rate from June 2010 to April 2021. If standard normal distributed jump statistics are used, the jump probabilities of Korean won–US dollar are lower when jump occurrences are frequent, and the jump returns for Korean won–US dollar will be considerably underestimated. However, if we utilize maximum outlying jump statistics, the jump probabilities of Korean won–US dollar are much higher. Furthermore, if we include periodicity filters such as median absolute deviation (MAD), shortest half scale (ShortH), and weighted standard deviation (WSD) in the maximum outlying jump statistics, the five-minute returns of Korean won–US dollar have considerably lower jump probabilities. Thus, the jump probabilities of Korean won–US dollar returns depend on whether standard normal distributed jump statistics or outlying jump statistics are used with periodicity filters such as MAD, ShortH, and WSD, in jump periods. Therefore, outlying jump statistics with periodicity filters such as ShortH and WSD ought to be used to obtain more consistent jumps probabilities for volatility and frequent jumps in the foreign exchange rate returns of 2010–2021.

Experimental and numerical settlement analysis of railway track over geogrid reinforced ballast

PurposeThe main objective of the present research is to investigate the benefits of using geogrid reinforcement in minimizing the rate of deterioration of ballasted rail track geometry resting on soft clay and to explore the effect of load amplitude, load frequency, presence of geogrid layer in ballast layer and ballast layer thickness on the behavior of track system. These variables are studied both experimentally and numerically. This paper examines the effect of geogrid reinforced ballast laying on a layer of clayey soil as a subgrade layer, where a half full scale railway tests are conducted as well as a theoretical analysis is performed.Design/methodology/approachThe experimental tests work consists of laboratory model tests to investigate the reduction in the compressibility and stress distribution induced in soft clay under a ballast railway reinforced by geogrid reinforcement subjected to dynamic load. Experimental model based on an approximate half scale for general rail track engineering practice is adopted in this study which is used in Iraqi railways. The investigated parameters are load amplitude, load frequency and presence of geogrid reinforcement layer. A half full-scale railway was constructed for carrying out the tests, which consists of two rails 800 mm in length with three wooden sleepers (900 mm × 90 mm × 90 mm). The ballast was overlying 500 mm thick clay layer. The tests were carried out with and without geogrid reinforcement, the tests were carried out in a well tied steel box of 1.5 m length × 1 m width × 1 m height. A series of laboratory tests were conducted to investigate the response of the ballast and the clay layers where the ballast was reinforced by a geogrid. Settlement in ballast and clay, was measured in reinforced and unreinforced ballast cases. In addition to the laboratory tests, the application of numerical analysis was made by using the finite element program PLAXIS 3D 2013.FindingsIt was concluded that the settlement increased with increasing the simulated train load amplitude, there is a sharp increase in settlement up to the cycle 500 and after that, there is a gradual increase to level out between, 2,500 and 4,500 cycles depending on the load frequency. There is a little increase in the induced settlement when the load amplitude increased from 0.5 to 1 ton, but it is higher when the load amplitude increased to 2 ton, the increase in settlement depends on the geogrid existence and the other studied parameters. Both experimental and numerical results showed the same behavior. The effect of load frequency on the settlement ratio is almost constant after 500 cycles. In general, for reinforced cases, the effect of load frequency on the settlement ratio is very small ranging between 0.5 and 2% compared with the unreinforced case.Originality/valueIncreasing the ballast layer thickness from 20 cm to 30 cm leads to decrease the settlement by about 50%. This ascertains the efficiency of ballast in spreading the waves induced by the track.

Topography‐Based Particle Image Velocimetry of Braided Channel Initiation

AbstractRiver channels shape landscapes through gradual migration and abrupt avulsion. Measuring the motion of braided rivers, which have multiple channel threads, is particularly challenging, limiting predictions for landscape evolution and fluvial architecture. To address this challenge, we extended the capabilities of image‐based particle image velocimetry (PIV)—a technique for tracking channel threads in images of the surface—by adapting it to analyze topographic change. We applied this method in a laboratory experiment where a straight channel set in non‐cohesive sediment evolved into a braided channel under constant water and sediment fluxes. Topography‐based PIV successfully tracked the motion of channel threads if displacements between observations were less than the channel‐thread width, consistent with earlier results from image‐based PIV. We filtered spurious migration vectors with magnitudes less than the elevation grid spacing, or with high uncertainties in magnitude and/or direction. During braided channel initiation, migration rates varied with the channel planform development, showing an increase as incipient meanders developed, a decrease during the transitional braiding phase, and consistently low values during the established braiding phase. In this experimental setup, migration rates varied quasi‐periodically along stream at the half scale of initial meander bends. Lateral migration with respect to the mean flow direction was much more pronounced than streamwise migration, accounting for approximately 80% of all detected motion. Results demonstrate that topography‐based PIV has the potential to advance predictions for bank erosion and landscape evolution in natural braided rivers as well as bar preservation and stratigraphic architecture in geological records.

Flexural behavior of high strength concrete shallow wide beams reinforced by hybrid longitudinal reinforcement

ABSTRACT One of the most common statistical systems used in structures especially for wide span slabs are ribbed slabs with shallow wide beams (SWB). This experimental study aimed to investigate and enhance the flexural behavior of high-strength concrete SWB using hybrid longitudinal reinforcement from steel and advanced composite materials as a tensile main reinforcement in SWB. Longitudinal advanced composite bars locally manufactured from ribbed glass fiber reinforced polymer (GFRP) and the second type was ribbed basalt fiber reinforced polymer (BFRP). A group of six half scale SWB were examined in structures laboratory of American University in Cairo with dimensions 2.1 × 0.6 × 0.25 m for length (L), width (B) and depth (d) respectively with constant size effect (d/B). The first three specimens were completely reinforced at tension side with Steel, GFRP or BFRP ribbed bars to be considered a control specimen. Use of GFRP and BFRP bars enhanced the flexural capacity of SWB with 41% and 43% respectively compared to specimen completely reinforced with steel. But on the other hand, the crack propagation of specimens completely reinforced with GFRP and BFRP developed more quickly and had larger crack width compared to specimen completely reinforced with steel. Hybrid reinforcement from Steel with GFRP, Steel with BFRP and Steel with GFRP and BFRP specimens are used to enhance the crack pattern and mode of failure without a significant loss in flexural capacity of SWB. The flexural capacity of these three specimens was enhanced with 26%, 30% and 41% with a significant enhancement in crack pattern and ductility.

Effect of boundary element detailing on the seismic performance of reinforced concrete masonry shear walls

Laboratory tests demonstrated that reinforced masonry shear walls (RMSWs) can provide sufficient strength and ductility to be considered an efficient seismic force resisting system (SFRS) for mid-rise buildings. The ductility and overall seismic performance of shear walls were increased by providing confinement to the end zones of the walls to form boundary elements (BEs)., which enhanced the ultimate masonry compressive strain and curvature ductility of the walls. Regular stretcher blocks are commonly used in the construction of masonry boundary elements; however, they impose some constraints due to their geometrical characteristics. This study investigated the construction and testing of three half scale specimens of reinforced masonry shear walls with boundary elements (RMSWs+BEs) that were characterized by flexural dominance under reversed cyclic moment and lateral loading. In the lower story panel of a 12-story RMSW building, these walls constitute the plastic hinge zone, which is represented by a plastic hinge wall. In this study, C-shaped masonry units were used instead of stretcher units to construct BEs with different sizes and vertical reinforcement ratios. The findings of this work revealed that employing C-shaped masonry units to construct the BEs was effective in overcoming the construction limits imposed by stretcher units. Additionally, the results of this study demonstrated that when RMSWs+BEs are subjected to quasi-static reversed cyclic loading, they are capable of providing a high level of ductility with minimal loss of strength.

Analysis on the relationship between short-term variability and the weakening AMOC

The Atlantic Meridional Overturning Circulation (AMOC) is a vital component of the global climate system, playing a crucial role in transporting heat and salinity from the equator to the North Atlantic, which in turn keeps Europe significantly warmer than other regions at the same latitude. Despite the fact that long-term observations and models have demonstrated an AMOC slowdown in response to global warming since the industrial revolution, detecting this slowdown in the brief observational record has proven to be challenging. In this study, the author investigates the relationship between short-term variability and the weakening AMOC by analyzing satellite remote sensing data of sea surface salinity collected over a decade. As a consequence of global warming, the weakened AMOC transports less heat and salt from the equator to sub-polar regions, causing heat and salt anomalies. This evidence further corroborates the slowing of the AMOC in response to human-caused warming and emphasizes the variability on a scale of half a decade caused by the deceleration.

A mixed numerical-experimental study of the outdoor wind effects on the indoor air distribution under the multi-nozzle air curtains

The infiltration of cold air through the open doors is controlled using air curtains, resulting in lower thermal loss and higher energy efficiency in the buildings. Meanwhile, severe outdoor conditions affect the performance of the air curtains drastically. In this context, the performance of a multi-nozzle air curtain with two different geometries has been investigated under various outdoor conditions using validated CFD. The air curtain system creates a thermal barrier with a specific sequence of large nozzles, small nozzles, and holes that blow air downward at different speeds. A half scale (1:2) model located above a door in the middle of the wind tunnel at the University of Sherbrooke is used for the hot wire measurements of the critical characteristics for different wind velocities (0, 4, and 9 m/s). Also, the SST k−ω turbulence model has shown the highest accuracy during the turbulence model sensitivity analysis and is used for complementary studies. Despite all the similarities, the results indicate that Fifth Order Polynomial Nozzles are more resistant against the high-velocity front winds, comparing the Arc Shape Nozzles, due to 3.6% augmentation of the exit velocities at large nozzles and shorter convergence areas. Also, this fact is proven by the studies of the impact point of these air curtains.

Analysis on the effects of ecological conservation redline policies in the Pearl River Delta area, China

IntroductionThe ecological conservation redline (ECR) policies conducted in China are an important innovation to protect biodiversity, safeguard ecological security, and achieve sustainable development. The Pearl River Delta (PRD) area implemented the ECR policies in 2005.MethodsThis study examines the contrast between the 15 years before and after 2005. It also reveals the ECR policies' effects by comparing land use change, landscape pattern index, and habitat quality inside (IECR) and outside (OECR) the ECR area. Results and discussionThe results suggest that: (1) The ECR area has served as an ecological barrier in maintaining the stability of natural ecosystems. Over the past 30 years, the PRD area significantly changed land use types and ecosystems, mainly concentrated in the central plains and estuaries. Specifically, in the IECR, land use change was relatively stable, with a decrease of 0.05% and 0.57% in ecological land and an increase of 0.28% and 0.68% in construction land before and after 2005. In contrast, the OECR area land use changed dramatically, with a decrease of 0.37% and 1.36% in ecological land and an increase of 7.06% and 5.02% in construction land before and after 2005. (2) A general trend of landscape fragmentation exists in the study area. The contagion (CONTAG) in the IECR area is higher than in the OECR. The Shannon's diversity index (SHDI) in the IECR is lower than in the OECR area, which indicates a high degree and rapid landscape fragmentation in the OECR area. (3) Over 85% of the IECR scale had a habitat quality of 0.8–1, while the OECR area had an almost half scale with a habitat quality of 0–0.2. On the whole, the ecological stability and landscape connectivity of in the IECR area was higher than that of the OECR area. This indicates that the prohibitions on human disturbance, industrial construction, and logging activities in the IECR area allow green vegetation to succumb under natural conditions. Habitat quality in the IECR area was also higher than that of the OECR area in the PRD area, revealing that the quality of green development in the IECR area was higher. Finally, the ECR policies’ implementation has protected the environment in the PRD area and will provide experience for ecological conservation in other areas.

Cyclic Response of Sloped Extended End-Plate Moment Connections

Bolted extended end-plate (BEEP) moment connections are extensively recommended in design standards to be used as a prequalified beam-to-column connection in steel portal frames and special moment frame buildings. These standards assume that in such a connection, the beam is perpendicular to the steel column or that the slope angle of the steel beam is very small. To expand the engineering applications of BEEP connections in large-slope angle buildings, in this study, three one-sided specimens at half scale with 0°, 15°, and 30° slope angles, respectively, were designed and tested under cyclic loading. All dimensions of these specimens were identical, except the slope angles of their steel beams. The experimental results showed that the maximum rotation angles of these sloped BEEP connections exceeded 0.05 rad, and they were remarkably larger than those of other types of sloped rigid-moment connections tested by Mashayekh and Uang. However, the force concentration that occurred in the flange at the heel location was similar to that observed by them, and it led to the development of brittle fractures. Particularly, with the increase in the slope angle, the force concentration tended to become more severe. Three strengthening schemes for reducing the force concentration and enhancing the deformation capacities of the sloped BEEP connections subjected to the extremely rare earthquake, i.e., less than 2% probability of exceedance in 50 years, were evaluated using the finite element approach. These were Scheme I: stiffening the rib in the acute-angle zone, Scheme II: employing a reduced beam section (RBS) connection, and Scheme III: forming a curved web cut in a non-RBS beam. The analytical results showed that the three schemes decreased the von Mises stress level in the acute-angle zone of the connection web. Scheme I enhanced the initial rotation stiffness, flexural strength, and deformation rotation capacity. For Scheme II, a RBS configuration was employed, which effectively improved the connection rotation capacity, whereas it decreased the flexural strength of the sloped BEEP connection. Scheme III without a reasonable design led to a degradation of the hysteretic performance, moderate rotation capacity, and low flexural strength. Therefore, Schemes I and II leading to much better seismic behavior than Scheme III are recommended.

Experimental study on the effects of scale on the static and dynamic behaviour of Glulam and hybrid-Glulam beams

The research and development of timber and timber-hybrid systems depends heavily on the testing of large or full-scale structural components, which is often limited by laboratory space and budget constraints. Testing of small-scale samples is an alternative approach which can avoid costly experimental campaigns; however, little is known about evaluation of serviceability performance measures, including natural frequency and stiffness, which typically govern the design of elements in timber and timber-hybrid long-span systems. Downscale testing of timber is known to be susceptible to changes in material properties with size, the so-called ‘size effect’, but existing research into the size effect in timber focuses on strength rather than serviceability parameters. This work explores the effect of scaling down Glulam and hybrid carbon fibre (CFRP) reinforced Glulam beams, by comparing the dynamic and static performance of beams tested at both full-scale and approximately half scale. Outcomes of this experimental study indicate that serviceability parameters present small variations with scale, whereas strength parameters are affected by size effect in being consistently smaller in the full-scale samples when compared to their small-scale versions. It was also observed that tension-only reinforcement in hybrid CFRP–timber beams appeared to reduce the size effect in both static and dynamic parameters.

CNN Model with Multilayer ASPP and Two-Step Cross-Stage for Semantic Segmentation

Currently, interest in deep learning-based semantic segmentation is increasing in various fields such as the medical field, automatic operation, and object division. For example, UNet, a deep learning network with an encoder–decoder structure, is used for image segmentation in the biomedical area, and an attempt to segment various objects is made using ASPP such as Deeplab. A recent study improves the accuracy of object segmentation through structures that extend in various receptive fields. Semantic segmentation has evolved to divide objects of various sizes more accurately and in detail, and various methods have been presented for this. In this paper, we propose a model structure that reduces the overall parameters of the deep learning model in this development and improves accuracy. The proposed model is an encoder–decoder structure, and an encoder half scale provides a feature map with few encoder parameters. A decoder integrates feature maps of various scales with high area details and forward features of low areas. An integrated feature map learns a feature map of each encoder hierarchy over an area of previous data in the form of a continuous coupling structure. To verify the performance of the model, we learned and compared the KITTI-360 dataset with the Cityscapes dataset, and experimentally confirmed that the proposed method was superior to the existing model.

Research and development of three-dimensional isolation system for SFR (Experimental study on static characteristics using half scale size model)

Research and development of three-dimensional isolation system for SFR (Experimental study on static characteristics using half scale size model)

Repair of Damaged Continuity Joints Using Ultra-High Performance, Fiber Reinforced Self-Consolidating, and Magnesium–Aluminum–Liquid–Phosphate Concretes

Bridge elements known to develop damage over time are individual continuity joints connecting girders. Replacing damaged joints is an expensive and invasive process and a need exists to design a less invasive repair method. This study focused on evaluating an encapsulation repair method for continuity joints that would not require extensive demolition of the bridge deck to implement and could potentially be constructed without bridge closure. Approximately half scale connected bridge girder specimens were constructed and purposely damaged to create similar crack patterns to those seen in bridges. Once damaged, a set of three specimens was repaired using the encapsulation method with three different high performance materials, ultra-high performance concrete (UHPC), fiber reinforced self-consolidating concrete (FRSCC), and magnesium–aluminum–liquid–phosphate (MALP) concrete. Of the three repaired specimens for each material, one was tested in positive moment bending and two in negative moment bending, similar to in situ conditions. The results appear to indicate that using each of the tested materials as an encapsulation repair for damaged continuity joints is viable to re-establish continuity and load capacity. However, the UHPC repairs’ resistance to cracking could indicate the best performance by further protecting the continuity joint reinforcing steel from water ingress.

Development of Cyclic Stress-Strain Curves for Modified Rat-Trap Bond Concrete Brick Masonry from Experimental Investigations

Abstract: Present study is based upon the experimental results obtained by reloading and unloading of concrete brick masonry samples constructed in modified rat-trap bond under uniaxial compression perpendicular to their bed joints. Considering the advantage of air gap between perpends for thermal comfort, Flemish bond was modified as rat-trap bond using half scale modular bricks (95mm × 95mm × 45mm) and called Modified Rat-Trap bond concrete brick masonry. The air gap created within the wall was filled up with insulating material thermocol (Expanded polystyrene). General polynomial expression has been developed for both reloading and unloading curves separately which were found suitable to predict the behavior of said masonry at any given residual strain. With the help of this parent polynomial, the particular reloading and unloading curves are then developed by transferring the parent equation to stress-strain coordinate. It was observed that the nature of reloading and unloading curves is primarily influenced by plastic strain. A fair consistency was observed between the experimental and computed curves. Keywords: Uniaxial, Perpend, Wallet, Monotonic, Common Point, Stability Point,

Volatility Jump of Multi-Power and Maximum Outlyingness with Periodicity Filters in China yuan/US dollar Exchange Rates

The discrete daily and intraday jump probabilities of China yuan/US dollar returns from June 1, 2012 to April 30, 2021 is analyzed using five-minute returns considering periodicity filters of volatility. When we use Z-daily jump using either tripower quarticity and quadpower quarticity, the daily jump probability seems to be 66% and 70%, respectively, at α = 0.999. Thus, if the periodicity filters of volatility are not considered, the jump probabilities may be overestimated. When we use the intraday observations or periods, with the periodicity filters of volatility such as such as MAD and short half scale, the daily jump probability seems to be 39% and 40% at α = 0.999, respectively. When we consider the periodicity filters of volatility, the five-minute returns of China yuan/US dollar exchange rates have considerably lower daily jump probabilities than we use using max outlying daily jump statistics without MAD periodicity filters of volatility.

Research and Development of Three-Dimensional Isolation System for SFR

The development of a SFR(:Sodium-cooled Fast Reactor) is carried out by Japan Atomic Energy Agency and others. Not only the decrease of horizontal seismic loads, but also the decrease of vertical seismic loads is important in SFR which has thin wall structures. Accordingly, the three-dimensional isolation system is developed for the seismic design of the components. This isolation device consists of a thick rubber bearing, four coned disc spring units, four vertical oil dampers, eight sliding functions and a supporting function. Furthermore, horizontal oil dampers are installed for damping force. This isolation device has few critical development elements and no additional function such as the rocking suppression device. In this isolation system, the natural frequency in the horizontal direction is 0.29Hz, the natural frequency in the vertical direction is 3.0 Hz. This isolation device is premeditatedly developed from 2017. This project has carried out load tests with full and half scale coned disc springs. The design method of coned disc spring units has been confirmed. Furthermore, this project has developed the horizontal oil damper of high allowable velocity and the vertical oil damper. This project is carrying out load tests of the half scale three-dimensional seismic isolation device, which consist of the thick rubber bearing, the coned disc spring units, the supporting function and so on. The development of this isolation device will be continued sequentially. The fundamental design method of this isolation device is confirmed in this project.

Research and Development of Three-Dimensional Isolation System

The design basis ground motions have been revised to improve the seismic resistance of nuclear power plants. The reduction of seismic forces not only horizontally but also vertically has required more critical than in the past to ensure the seismic resistance of components. Notably, the design of a Sodium-Cooled Fast Reactor will require reducing the seismic forces applied to the components because of the components with thin wall thickness. To overcome this problem, the authors have been developed an innovative three-dimensional seismic isolation system. This seismic isolation system will be applied to the reactor building, as the isolated reactor building. Investigating the force and displacement relationships of this seismic isolation system is an essential process to verify the feasibility of the design for the isolation system. The static loading tests were conducted to verify the force and displacement relationships in horizontal and vertical directions, which used a half scale three-dimensional isolation system. This paper demonstrates that the horizontal supporting function enables a stable load path and the independence of the force and displacement relationships in horizontal and vertical directions to ensure even under simultaneous horizontal and vertical loading assumed in the design basis ground motion.

Numerical and experimental performance evaluation of upgraded knee braces under cyclic load

In this paper, the seismic performance of the structure is analyzed by introducing a new angular knee element. Cyclic loads are applied to determine the seismic performance. The result is compared with a vertical knee element. The angular knee element showed better seismic performance as compared to the vertical knee element. The new short knee element studied in two positions including 1- a vertical knee element perpendicular to cross-brace is called VSKE 2- An angular knee element that is called ASKE. Using reduced knee section specimens for better performance. Effect of Angular knee element in knee-braced frames (KBFs) under Cyclic Loading was investigated by testing using a half scale specimen mounted on a reaction frame at two positions including horizontally for VSKE and inclined for ASKE. For experimental tests, specimens were loaded by using a hydraulic actuator. Finite element modelling was used for the simulation of detailed behavior using a verified experiment base model. It has been shown that the performance of knee element fuses can improve the ductile behavior of knee braced frames. Based on the results of vertical and angular cases, it has been shown that an increase of angle between main cross brace and short knee element (incline specimen) can reduce maximum equivalent plastic strain (EPEQ) in the web of knee element fuse.

An Experimental Performance Evaluation for a Swirl-Vane Separator Using an Air-Water Test Facility

The most important design parameters of a moisture separator to optimize the efficiency of a nuclear power plant are the moisture carry over and pressure drop. An air-water test facility was constructed to evaluate the design parameters for various types of conventional moisture separators in Korea. In this study, a half scale of swirl-vane separator was designed, and test conditions were defined based on the scaling law to cover a wide range of operating conditions. The moisture carry over was measured using an isokinetic sampling system for 34 different flow conditions. The MCO was in range of 0.30–7.05% according to the test conditions. Single and two-phase flow experiments were also carried out to identify the two-phase pressure drop characteristics. Based on the obtained results, the proposed empirical correlation model was extended to a submerged separator and applying these results to a full scale system is discussed in this paper.

Experimental investigation of the shear strength of one‐way reinforced concrete (RC) slabs subjected to concentrated loads and in‐plane transverse axial tension

AbstractThis paper presents the results of an experimental campaign carried out to investigate the effects of in‐plane transverse tensile forces on the shear strength of linearly supported one‐way reinforced concrete (RC) slabs without shear reinforcement subjected to concentrated loads. A total of 5 half scale slabs (1650 × 1650 × 120 mm), subjected simultaneously to different levels of in‐plane tensile forces and a concentrated load were tested up to failure. The clear shear span to effective depth ratio av/d was equal to 3 in all tests, to minimize the effects of the direct transmission of the load to the closest support, the so called arching action. As observed, the shear strength barely decreases with increasing values of the tensile force applied, even for values of the external force that cracked the concrete cross‐section of the slabs in the direction perpendicular to the span. These observations may indicate that the shear–flexural behavior in the spanning direction is not significantly affected by the membrane forces in the transverse direction.