Negative Displacement Research Articles

Robots and industrial labor: Evidence from Japan

This paper provides one of the first studies of the impact of the introduction of robots to equilibrium labor demand in an entire economy. We use long-term (1979–2012) industry-level panel data from Japan, a country that is over 10 times as intensive in the use of robots as in the U.S. Our model, which is derived from Acemoglu and Restrepo (2017), shows that there are three effects on labor demand in the aggregate economy from the introduction of industrial robots. The first is the negative displacement effect of robots taking over the tasks of humans. The second is the positive industry productivity effect of robots lowering costs in a particular industry. This lowering of costs draws demand to the industry and expands output and employment in that industry. The third is the positive general equilibrium effect. Robots raise productivity and expands demand in all industries, thereby increasing the product and labor demand for the industry introducing the robots. In our estimation, we find that the displacement effect is insignificant, the productivity effect is sometimes positively significant, and the macroeconomic general equilibrium effect is always highly positively significant. Overall, the introduction of robots has been beneficial to the demand for labor in Japan. Our results are robust to various controls and instrumental variables.

Robots and Industrial Labor: Evidence from Japan

This paper provides one of the first studies of the impact of the introduction of robots to equilibrium labor demand in an entire economy. We use long-term (1979-2012) industry-level panel data from Japan, a country that is over 10 times as intensive in the use of robots as in the U.S. Our model, which is derived from Acemoglu and Restrepo (2017), shows that there are three effects on labor demand in the aggregate economy from the introduction of industrial robots. The first is the negative displacement effect of robots taking over the tasks of humans. The second is the positive industry productivity effect of robots lowering costs in a particular industry. This lowering of costs draws demand to the industry and expands output and employment in that industry. The third is the positive general equilibrium effect. Robots raise productivity and expands demand in all industries, thereby increasing the product and labor demand for the industry introducing the robots. In our estimation, we find that the displacement effect is insignificant, the productivity effect is sometimes positively significant, and the macroeconomic general equilibrium effect is always highly positively significant. Overall, the introduction of robots has been beneficial to the demand for labor in Japan. Our results are robust to various controls and instrumental variables.

Simultaneous 10 kHz three-dimensional CH2O and tomographic PIV measurements in a lifted partially-premixed jet flame

High-speed, three-dimensional (3D) scalar-velocity field measurements are demonstrated in a lifted partially-premixed dimethyl-ether/air jet flame using simultaneous laser-induced fluorescence (LIF) of formaldehyde (CH2O) and tomographic particle image velocimetry (TPIV). The 3D LIF measurements are performed by raster scanning the laser beam from a 100 kHz pulse-burst laser across the probe volume using an acousto-optic deflector. The volumetric reconstruction of the LIF signal from ten parallel planes provides quasi-instantaneous 3D LIF measurements that are synchronized with 10 kHz TPIV measurements. The temporally resolved CH2O-LIF and velocity field data are used to analyze Lagrangian particle trajectories and displacement speeds at the base of the lifted flame. The particle trajectories reveal flow structures that are difficult to observe in an Eulerian reference frame. Positive and negative displacement speeds are observed at the CH2O-LIF surfaces at the inner and outer regions of the jet flame with a maximum displacement speed of approximately eight times the laminar flame speed of a stoichiometric dimethyl-ether/air mixture. The observations in present study support formation of lean premixed flames near the flame base whose role in flame stabilization should be investigated in more detail.

An optimized roots power machine based on negative displacement theory

Roots power machine has obvious advantages in low and medium temperature waste heat recovery. The existing roots power machine has the problem of internal flow field disturbance, which seriously affects the power generation efficiency of the power machine. In order to solve the problem of disturbance of the internal flow field of roots power machine, the traditional involute rotor roots power machine is improved, and the roots power machine based on negative displacement involute rotor is proposed. The structure model and turbulence model of roots power machine are constructed, and the internal flow field simulation of roots power machine is realized by CFD. The pressure contour and torque change of roots power machine before and after improvement are compared, and the experimental research on the improved structure is carried out. The results show that the intensity of flow field disturbance in the modified involute rotor roots power machine decreases, and the working performance of the roots power machine improves,which provides a reference for the structural improvement and performance optimization of roots power machine.

Effects of surface roughness on the aerodynamic performance of a high subsonic compressor airfoil at low Reynolds number

The aerodynamic performance of compressor airfoil is significantly affected by the surface roughness at low Reynolds number (Re). In the present study, numerical simulations have been conducted to investigate the impact of surface roughness on the profile loss of a high subsonic compressor airfoil at Re = 1.5 × 105. Four roughness locations, covering 10%, 30%, 50% and 100% of the suction surface from the leading edge and seven roughness magnitudes (Ra) ranging from 52 to 525 μm were selected. Results showed that the surface roughness mainly determined the loss generation process by influencing the structure of the Laminar Separation Bubble (LSB) and the turbulence level near the wall. For all the roughness locations, the variation trend for the profile loss with the roughness magnitude was similar. In the transitionally rough region, the negative displacement effect of the LSB was suppressed with the increase of roughness magnitude, leading to a maximum decrease of 14.6%, 16.04%, 16.45% and 10.20% in the profile loss at Ra = 157 μm for the four roughness locations, respectively. However, with a further increase of the roughness magnitude in the fully rough region, the stronger turbulent dissipation enhanced the growth rate of the turbulent boundary layer and increased the profile loss instead. By comparison, the leading edge roughness played a dominant role in the boundary layer development and performance variation. To take fully advantage of the surface roughness reducing profile loss at low Re, the effects of roughness on suppressing LSB and inducing strong turbulent dissipation should be balanced effectively.

Objective visualization of the effect of different knee flexion angles on medial-lateral displacement of the knee center in frontal plane during single-Leg Squat

Introduction:The subjective single-leg squat (SLS) test can be used as a functional diagnostic agent to prevent knee injuries. [1] However, there are missing objective data about its functional rating, performance, squat depth and medio-lateral knee displacement in the frontal plane. [2] There-fore, the purpose of this pilot study was to evaluate the medio-lateral knee displacement in the frontal plane with a 3D motion capture system at different knee flexion angles during the SLS in healthy patients.Hypotheses:The hypothesis was that according to different knee flexion angles, there is a variability of medial knee displacement (= valgus positions) in healthy patients.Methods:17 healthy and sporty subjects (9 ♀/ 8 ♂, age 25±4 years, BMI 24±2 kg/m2) participated in this study. Exclusion criteria were balance disorders, hip knee and/ or ankle complaints, sur-gery history, high deviation in lower extremity axis (i.e. Genu varum/ Genu valgus). Knee dis-placement was measured by 3D motion analysis system (Vicon Motion Systems, Oxford, UK) using a modified method of Krosshaug et al. [3] Thus, knee displacement was defined as distance between knee joint center and reference plane including the calculated hip and ankle joint center and the fixed toe marker on the second metatarsal head. A positive knee dis-placement was associated with a knee valgus, a knee varus was described as negative knee displacement. Every participant did 12 single-leg squats on each side.Results:The following knee flexion angles of all SLSs were captured (°, mean and standard deviation (±)): start position at 11 ± 6; downward phase at 40 ± 0 and 60 ± 0; maximum at 86 ± 16; up-ward phase at 60 ± 0 and 40 ± 0; end position at 8 ± 6. The medio-lateral knee displacement of all SLSs showed at the mentioned knee flexion an-gles the following values respectively (mm, median, interquartile range (25th - 75th quartile)): -12 (-19 to -5); 0 (-9 to 7); 13 (-2 to 28); 38 (8 to 61); 17 (0 to 36); 4 (-6 to 16); -15 (-22 to -7).Conclusion:According to different knee flexion angles, there is a variability of medio-lateral knee dis-placements in healthy patients. This variability should be included in the functional rating of a SLS as well as in the interpretation of different knee pathologies. Moreover, it provides an objective basis in the prediction of knee injuries.

Numerical Modeling of Particles Separation Method Based on Compound Electric Field

This paper shows the results of simulation of features and usability of a proposed method for particle matter (PM) separation detection based on composite electric field. Considering the composite electric field and drag coefficient, a nonlinear dynamic model of particle separation is established. Meanwhile, the model takes into account the changes in the dynamic model caused by the different diameters and different speeds of the particles, and uses the effect of the composite electric field to separate the PM. Numerical simulation results show that the PM diameter, electric field strength, and drag force have significant effects on the separation of particles. Among them, as the drag force decreases, the particle separation displacement gradually increases, and the electric field affects the particle separation direction. In the acceleration room, the particle velocity increases with the increasing of the electric field strength. In the separation room, the displacement of the particulate matter in the Y-axis direction gradually increases from a negative displacement to a positive displacement as the electric field strength increases. The displacement forms a bow shape. When the drag coefficient is changed, the displacement will suddenly increase while it is lower than a certain value. Considering the change of electric field and drag force at the same time, the separation effect would be more obvious when the drag coefficient is smaller. The electric field strength affects the separation direction of the particulate matter.

Goos–Hänchen shift produced by a one-dimensional photonic crystal doped with InSb

In this paper, a novel kind of one-dimensional (1D) photonic crystal (PC) doped with indium antimonide (InSb) is proposed, which is theoretically investigated by the transfer matrix method to create a giant lateral shift that is also called the Goos–Hänchen (GH) shift. The transmittance features of the proposed PCs are ascribed to the temperature. The influences of the incident angle on the transmittance of TE and TM waves have also been studied in the theory. For the TE wave, the transmittance is also affected by magnetic field strength, due to the characteristics of the permittivity of InSb layers. Therefore, for the TE wave, such PCs not only can generate huge positive and negative GH displacements but also can produce some regular changes under the effects of temperature and external magnetic field. The calculated results demonstrate that the normalized positive GH shift can reach around 55 times the wavelength, and the normalized negative one can get to around 182 times the wavelength. When the angle of incidence is large or small, the resulting GH shift will also produce interesting changes. These 1D PCs may provide a theoretical possibility for some devices that detect changes in temperature or magnetic field strength, or may be applied to angle sensors.

Three Dimensional Analysis of Raft Foundation Rest on Homogenous Soil Using Finite Element Method

The study includes analysis of Al – Samaraie Hospital raft foundation by the finite element method (FEM) using program package Fear 4.0. The analysis conducted on the foundation is resting on infinite, homogeneous, isotropic soil. In this study, effect of raft thickness, soil properties, modulus of elasticity and Poisson’s ratio of soil are investigated. The most dominant parameters such as thickness of raft foundation, modulus of elasticity and Poisson’s ratio of soil are graphically plotted against maximum displacements, maximum positive and negative bending moments (Mx, My and Mxy). The results showed that raft thickness and soil properties play a vital role in changing the values of maximum positive and negative moments (Mx, My) and maximum displacements, while their effect on maximum positive and negative moment (Mxy) can be considered as insignificant. Also, empirical equations have been developed to calculate maximum positive and negative bending moment (Mx, My) and maximum displacements beneath the raft. This is performed by the aid of statistical program (Statistic). The accuracy of the proposed equations was ranging between 92.7% and 99.9%.

Mg2+ Is a Missing Link in Plant Cell Ca2+ Signalling and Homeostasis-A Study on Vicia faba Guard Cells.

Hyperpolarization-activated calcium channels (HACCs) are found in the plasma membrane and tonoplast of many plant cell types, where they have an important role in Ca2+-dependent signalling. The unusual gating properties of HACCs in plants, i.e., activation by membrane hyperpolarization rather than depolarization, dictates that HACCs are normally open in the physiological hyperpolarized resting membrane potential state (the so-called pump or P-state); thus, if not regulated, they would continuously leak Ca2+ into cells. HACCs are permeable to Ca2+, Ba2+, and Mg2+; activated by H2O2 and the plant hormone abscisic acid (ABA); and their activity in guard cells is greatly reduced by increasing amounts of free cytosolic Ca2+ ([Ca2+]Cyt), and hence closes during [Ca2+]Cyt surges. Here, we demonstrate that the presence of the commonly used Mg-ATP inside the guard cell greatly reduces HACC activity, especially at voltages ≤ −200 mV, and that Mg2+ causes this block. Therefore, we firstly conclude that physiological cytosolic Mg2+ levels affect HACC gating and that channel opening requires either high negative voltages (≥−200 mV) or displacement of Mg2+ away from the immediate vicinity of the channel. Secondly, based on structural comparisons with a Mg2+-sensitive animal inward-rectifying K+ channel, we propose that the likely candidate HACCs described here are cyclic nucleotide gated channels (CNGCs), many of which also contain a conserved diacidic Mg2+ binding motif within their pores. This conclusion is consistent with the electrophysiological data. Finally, we propose that Mg2+, much like in animal cells, is an important component in Ca2+ signalling and homeostasis in plants.

Intracranial Pressure After Soccer Heading

OBJECTIVETo evaluate the effect of soccer heading on intracranial pressure (ICP) in trained athletes.METHODSEight subjects (all male, 21.7±1.7 years) were recruited from the UC San Diego soccer team. ICP and cardiovascular variables were recorded before and after 6 repeats of heading a soccer ball kicked from 35 yards away, into a goal. ICP was estimated non‐invasively from acoustical evoked tympanic membrane displacement (Vm), where a more negative volume displacement is correlated with higher ICP. Mean arterial pressure (MAP), heart rate (HR; Nexfin, Netherlands), and ICP were recorded in three different postures, 15° head up tilt (HUT), 0° supine, −15° head down tilt (HDT), in a randomized order.RESULTSMean Vm at 15° HUT was 37.81±133.21 nL at baseline and −20.82±158.27 nL immediately post soccer heading (P=0.0482, paired t test), analogous to an increased ICP. At 0° supine, mean Vm was −46.19±178.50 nL at baseline and −84.27±183.55 nL after impact (P=0.0321, paired t test). At −15° HDT, mean Vm was −148.48±196.07 nL at baseline and −187.02±186.19 nL immediately post soccer heading (P=0.1176, paired t test). MAP and HR did not significantly change between the baseline and post soccer heading measurements.DISCUSSIONAfter repeated soccer ball heading, ICP significantly increased at 15° HUT and 0° supine, while ICP at −15° HDT, MAP and HR did not significantly change. The relative increase in ICP associated with HDT is comparable to previously described trends. Although the measurement technique currently employed does not provide an absolute ICP baseline, the technique has been established as useful in evaluating relative changes. Under that interpretation, these results reflect what may be an elevated ICP related to soccer heading impacts. Accordingly, the results of this study suggest a potential health risk of participation in head contact sports.Support or Funding InformationNASA (80NSSC19K0020) and Novo Nordic Foundation (NNF16OC0019196)Soccer Heading Increases Intracranial Pressure at Head Up Tilt and Supine PositionsVolume displacement of tympanic membrane (Vm), measured non‐invasively from acoustical evoked tympanic membrane displacement, indicated an increase in intracranial pressure (ICP) after soccer heading at 15° head up tilt (HUT) and 0° supine (n = 8, paired t test, *P < 0.05). No significant increase in ICP at −15° head down tilt (HDT) was observed after soccer heading.Figure 1

Assessment of an Evolution Equation for the Displacement Speed of a Constant-Density Reactive Scalar Field

The displacement speed that characterises the self-propagation of isosurfaces of a reaction progress variable is of key importance for turbulent premixed reacting flow. The evolution equation for the displacement speed was derived in a recent work of Yu and Lipatnikov (Phys Rev E 100:013107, 2019a) for the case where the flame is described by a transport equation for single reaction progress variable assuming simple transport and one-step chemistry. This equation represents interaction of a number of complex coupled mechanisms related to straining by the velocity field, surface curvature and the scalar gradient. The aim of the current work is to provide detailed physical explanations of the displacement speed equation and its various terms, and to provide a new perspective to understand the mechanisms responsible for observed variations in the displacement speed. The equation is then used to analyze the propagation of a statistically planar reaction wave in homogeneous isotropic constant-density turbulence using direct numerical simulations. Additional emphasis is put on retracting surface segments that have a negative displacement speed, a phenomenon that commonly occurs at high Karlovitz numbers.

The transient response of a functionally graded half-space heated by a laser pulse based on the generalized thermoelasticity with memory-dependent derivative

Based on the generalized thermoelasticity with memory-dependent derivative, the transient response of a half-space heated by a non-Gaussian laser beam on its boundary is investigated. The coupled governing equations containing thermal time-delay factor and thermal kernel function, which can be chosen to adapt to specific problems, are formulated and solved by the Laplace transform technique and its numerical inversion. For the functionally graded half-space, its material properties are assumed to exponentially vary with material coordinate. In calculation, the non-dimensional temperature, displacement as well as stress under different thermal time-delay factor, thermal kernel function and functionally graded parameter are obtained and illustrated graphically. The results show that: with the decrease of thermal time-delay factor or the increase of exponent of thermal kernel function, the peak value of the non-dimensional temperature, displacement and the absolute value of peak value of stress increase; negative temperature value, positive displacement and stress values will appear when functionally graded parameter is less than zero. It is hoped that the obtained results would be helpful in designing the functionally graded materials heated by a non-Gaussian laser beam in engineering.

The determinants of the entrepreneurial triggering: a study of the graduated students from the National School of Engineering of Sfax

In many countries such as Tunisia business creation by young graduates is of major importance since it is supposed to stimulate growth and employment. This investigation explores three types of determinants of the entrepreneurial triggering: the entrepreneurial intention of the individuals, the positive displacements occurred in their lives and the negative displacements. We addressed a questionnaire to 665 young engineers from the Tunisian National School of Engineering of Sfax 3 years after they got their diploma in the academic year of 2012/2013. Eight-four respondents completed the questionnaire; 43% of them were engaged in an entrepreneurial process. Following the conceptual approach of Shapero and Sokol (in: Kent, Sexton, Vesper (eds), Encyclopedia of entrepreneurship, Prentice-Hall, INC, Englewood Cliffs, 1982) and DeGeorge and Fayolle (J Small Bus Enterp Dev 18(2):251–277, 2011), we mix the theory of planned behaviour and a situated action perspective to develop a structural model that we estimated with a partial least squares path model. The results indicate that there is a close-knit tie between intention and the entrepreneurial triggering which is coherent with a planned process of entrepreneurial decision-making. However, positive displacements related to economic opportunities have a positive and significant direct effect on triggering that is not mediated by the intention. According to the situated action perspective, it reveals that the process of entrepreneurial triggering is not fully determined by a traditional process of decision-making but also the direct result of contextual factors. Concerning negative displacements, their direct impact on the triggering is not significant but the sum of their direct plus indirect effects is positive and significant.

Tunable and enhanced Goos-Hänchen shift via surface plasmon resonance assisted by a coherent medium.

We present a scheme for enhancing Goos-Hänchen shift of light beam that is reflected from a coherent atomic medium in the Kretschmann-Raether configuration. The complex permittivity of the medium can be coherently controlled and has significant influence on the surface plasmon resonance (SPR) at the metal-medium interface. By tuning the atomic absorption, the internal damping of SPR system can be modulated effectively, thereby leading to giant positive and negative lateral displacements. The refractive index of medium determines the SPR angle. Thus the peak position of the beam shift becomes tunable. As the optical response of the coherent medium depends on the intensity and detuning of the controlling fields, we are able to conveniently manipulate the magnitude, the sign, and the angular position of Goos-Hänchen shift peaks.

Clinical impact of needle-free connector design: A systematic review of literature.

The objective of this systematic review is to analyze types of needle-free connectors and open systems and their effects on central line-associated bloodstream infection rates and other adverse outcomes through a research protocol consistent with the Preferred Reporting Items for Systematic Reviews' recommendations. MEDLINE and Cochrane databases of systematic reviews were searched for relevant comparative studies published from January 2000 to September 2017. Eighteen studies compared central line-associated bloodstream infection (according to the Centers for Disease Control and Prevention/National Healthcare Safety Network definition), internal microbial contamination, occlusions, phlebitis, and other outcomes associated with needle-free connectors with a positive displacement device, negative displacement device, neutral displacement device, or three-way stopcock. Ten studies reported central line-associated bloodstream infection rates, which were lower with positive displacement devices versus negative displacement devices/neutral displacement devices (one study) and with negative displacement devices versus three-way stopcocks (three studies), but varied with different positive displacement device and negative displacement device/neutral displacement device designs (four studies). Seven studies reported internal microbial contamination rates, which were higher with three-way stopcocks versus negative displacement devices (two studies) and positive displacement devices (two studies), lower when positive displacement devices were used versus neutral displacement devices (one study), and varied with different types of negative displacement device (one study). Central line-associated bloodstream infection rates and most other outcomes analyzed were statistically significantly higher with three-way stopcocks (open devices) versus positive displacement device, negative displacement devices, and neutral displacement devices, but varied among closed device designs.

Mapping of surface deformation associated with the 5.2 magnitude Stilfontein earthquake of 3 April 2017 using radar interferometry

This paper presents surface deformation associated with the 5.2 magnitude Stilfontein earthquake of 3 April 2017 using Sentinel-1 data. Analysis involved calculation of vertical displacement for two situations (unmasked and masked with a layer of coherence ≥0.6). The displacement for the unmasked situation ranged from −21 mm to +49 mm whereas with higher coherence of ≥0.6 it ranged from −18 mm to 45 mm. Major positive displacements of 32–45 mm observed in the KOSH region whereas negative displacements of −15 mm to −28 mm observed in the northern, north-eastern, north-western and south-western part of the image. Comparison of vertical displacement with geology indicated that the areas of high positive deformation or uplifts were in the central portion of the image underlain by the geological units of Malmani Subgroup, Rietgat Formation, Klipriviersberg Group, Dominion Group, Hospital Hill Subgroup, Allanridge Formation and Volksrust Formation. Areas of high negative deformation or subsidence are confined to the northern and north-eastern region underlain by Malmani Subgroup and north-western region underlain by Kameeldoorns Formation and south-western region underlain by Allanridge Formation. An attempt to compare the deformation and vertical displacement with isoseismal map revealed similarity/matching of higher surface deformation areas with the shapes and values of high value isoseismal contours. No major faults were seen at or near the epicentre of the earthquake. The surface deformation distribution associated with the occurred earthquake will help to identify possible areas of major deformation, if earthquake of same magnitude and depth of origin occurs in the same area in future.

An Applied Study on the Influence of the Vehicle Body Shape on Air Resistance

The current high-geared developments within the automotive sector have triggered a series of performance, comfort, safety and design-related issues. Hence, oftentimes manufacturers are challenged to combine various elements so as to achieve an attractive design, without diminishing the vehicle’s dynamic performance. Under the circumstances, the shape of the vehicle body becomes the key element that connects the design component with the performance requirement, since it directly influences the value of the resistance forces, and, respectively the air resistance. Aerodynamics is the branch of mechanical engineering that deals with the movement of gases (especially the air) and their effects on fluids. As far as the automotive sector is concerned, aerodynamics focuses mainly on the flow of the air currents over the vehicle body. When designing vehicle, the positive or negative displacement of the airflow is studied in aerodynamic tunnels. It is preferable for the negative displacement to push the vehicle as close to the ground as possible. In what follows we set out to study the influence of the drag coefficient and, implicitly, of the air resistance on vehicle performance. Hence, we will carry out comparative analysis of two vehicles with similar technical characteristics, but with different bodies, i.e. a hatchback and a sedan. The results obtained are then compared both by means of the analytical determination of the air resistance and via a simulation performed within the Virtual Crash software platform. The results recorded show that of the two vehicles, with the considered aerodynamic coefficients, hatchback type vehicle displays lower values in terms of air resistance.

Picturing beach erosion and deposition trends using PSInSAR: an example from the non-barred southern west coast of India

Coastal dynamics can rapidly alter beach morphology. In some places, such as the non-barred southern west coast of India, studying changes to beach morphology is a relatively arduous task. Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR), a remote sensing technique that utilizes stacks of radar images for accurate long-term monitoring of ground features, allows for detailed observations of coastal morphodynamics. Twenty-two single look complex (SLC) synthetic aperture radar (SAR) Sentinel-1A images, acquired from 4 March 2016 to 3 June 2017, are used to monitor geomorphological processes such as coastal erosion and deposition. Ground deformation measurements from PSInSAR processing shows the coast stretching ~ 70 km between Thaickal and Munambam is highly dynamic, characterized by phases of erosion and deposition. The highest negative displacement of − 24.9 mm at Thaickal versus the + 7.6 mm at Chellanam in the north show the co-existing milieus of erosion and deposition. PSInSAR results concur with corresponding Google Earth images. In addition, beach sediment texture and scanning electron microscope grain micro-texture in the beach segment further corroborate temporal phases of erosion and deposition. Two locations are identified as typical erosional sites, while one location typified deposition. Erosion and deposition or rebuilding of beaches, usually correspond respectively with the onset and offset of SW monsoon wave climate in the Arabian Sea. When zones of deposition are mainly located in the proximity of river and/or lake inlets, stretches characterized by erosion are distal to inlets. Linear regression analyses of displacement–time series plots were used to identify general erosion or depositional regimes along beach segments. Results from this study illustrate how PSInSAR is a capable and reliable processing tool for monitoring temporal phases of coastal morpho-dynamics.

New rocking column with control of negative stiffness displacement range and its application to RC frames

This paper investigates the use of rocking columns with central steel bars in RC building frames. Motivated by the adverse effects of conventional steel bars anchored at both ends, a new rocking column is proposed that allows the slippage of the steel bar at the bottom end within a controlled range of displacements (gap). A numerical model of the new rocking column is developed and implemented in Opensees. A parametric study is conducted to investigate the overall response of several RC frames featuring the proposed rocking columns in the first story. It was found that the response is controlled by (i) the maximum restoring force provided by the rocking columns, (ii) the lateral strength provided by the dampers, and (iii) the dimensions of the gap. In comparison with conventional RC frames, the proposed solution reduces the maximum inter-story drifts in the upper stories by about 3 times, the story accelerations about 1.5 times and the energy dissipation demand about 20 times. The results of this research are expected to enhance the use of rocking columns for seismic isolation of RC frame structures, through a new solution that takes full advantage of the negative stiffness and prevents collapse.