Narrow Results

The response of the side shell to non-contact underwater explosion is of major concern in ship design. While extensive research is carried out on air-backed plates, relatively less attention is paid to water-backed plates. Nevertheless, the response of the water-backed plates becomes relevant when the water filled side shells are exposed to an underwater shock loading. Availability of scant information on the experimental results of water-backed plates is the primary motivating factor to make analytical estimates. These estimates are provided in comparison with an air-backed plate for identical attack geometry and target parameters. This work aims to bring out a comparative procedure for the damage assessment between air- and water-backed plates so that the response of the latter can be presented in terms of that of the former.

Background: The biomechanical interaction between the median nerve and the flexor tendons is an important consideration in Carpal tunnel syndrome (CTS). We aim to quantify the displacement and compressive deformation pattern of the median nerve in various stages of finger flexion in the normal population at the inlet of the carpal tunnel. Methods: Transverse ultrasounds images were taken at the carpal tunnel inlet during full-extension, mid-flexion and full flexion. The displacement, distance, Feret's diameter, and perimeter of the median nerve were calculated and compared between each position. Results: Biphasic median nerve motion was observed, with a displacement of 2.84 ± 3.49 mm in the ulnar direction from full-extension to mid-flexion (Phase I) and a further 0.93 ± 3.04 mm from mid-flexion to full flexion (Phase II). Of 49 hands, 37 (75.5%) exhibited ulnar displacement in Phase I while 12 (24.5%) exhibited radial displacement. Feret's diameter (5.95 ± 1.08 mm) and perimeter (13.28 ± 2.09) of the median nerve were greatest in the mid-flexed position. Conclusion: In a healthy Asian population, the median nerve has a biphasic motion during finger flexion, with maximal deformation in the mid-flexed position.

Background: Vertebrae are linked together with facet and intervertebral joints. The application of a force to a spinal segment therefore impact adjacent areas of the spine. Objective: This study aimed to investigate the posteroanterior (PA) displacement of the thoracocervical spine during the application of thoracic PA mobilization. Methods: Forty-one healthy males were recruited. The participants were asked to lie prone and hold their breath at the end of normal expiration while a therapist applied a grade III of central PA mobilization to the T₆ spinous process for 30s. The PA spinal displacements of C₃, C₅, C₇, T₂, T₄ and T₆ were investigated using a motion capture system. Descriptive statistics and Pearson’s correlation coefficient were used to analyze the PA spinal displacement and correlation between PA spinal displacement at T₆ and the PA displacement of the thoracocervical spines, respectively. Results: The PA displacement of the T₆ and the PA displacement of the marked spines (T₄, T₁, C₇, C₅ and C₃) correlated well with $r$ being 0.83, 0.69, 0.63, 0.63 and 0.54 ($p<0.01$), respectively. A trend toward a decrease in spinal displacement was noted when the distance from T₆ spine increased. It showed that the mobilization force could be transferred from the local area to an adjacent area. Conclusions: These findings may provide plausible evidence that can explain the mechanism of how thoracic spinal manipulative therapy affects neck pain reduction.

Previously, it was found that the analytical deflections computed for towers using computer software are less than those from test results. The present study is aimed at deriving a relationship between the ratio of the test to theoretical deflection, and a nondimensional parameter to serve as an index for monitoring the structural displacements during testing. Currently, structural dynamic evaluation plays little or no role in the design of towers, partly due to the difficulties involved in the analysis and the relatively high cost of field testing. Using the fundamental frequency of a tower, the peak response of the tower to gusty wind and the impact force caused by conductor breakage can be evaluated. Both theoretical and experimental studies have been carried out to evaluate the natural frequencies of the towers tested at TTRS, SERC, Chennai, India. Based on these data, an equation was derived in this paper using the tower geometry and test/theoretical deflection ratios, which allows us to predict the natural frequency of the tower in a way closer to its actual value.

A self-anchored suspension bridge balances forces internally without external anchorage requirements, making it suitable for sites where anchorages would be difficult to construct. It often adopts either a full-floating or a semi-floating tower-girder connection system, which may result in large displacement responses along bridge longitudinal direction during earthquakes. This study investigated the efficacy of using the fluid viscous damper (FVD) for seismic control of a single-tower self-anchored suspension bridge. First, the energy dissipation behaviors of the FVD under sinusoidal excitations were studied. It revealed that besides the damper parameters (i.e. damping coefficient and velocity exponent) of an FVD itself, the energy dissipation capacity also relies on the characteristics of external excitations. Therefore, optimum damper parameters added to a structure should be determined on a case-by-case basis. Parametric study was then carried out on the prototype bridge, which indicated a tendency of decreasing the longitudinal deck/tower displacements and tower forces with increasing damping coefficient $C$ and decreasing velocity exponent $\alpha$. Compared with the linear FVD, the nonlinear FVD with a smaller velocity exponent can develop more rectangular force-displacement loops and thus achieve better energy dissipation performance. With selected optimum damper parameters (i.e. $C=3000$kN$\cdot$m${}^{-0.3}$s${}^{0.3}$ and $\alpha =0.3$) for the two FVDs added between the deck and the tower, the longitudinal deck and tower displacements could be reduced by 54%, while the peak bending moment and shear force at the tower base could be reduced by 30% and 19%, respectively. It is concluded that the nonlinear FVD can provide a simple and efficient solution to reduce displacement responses of self-anchored suspension bridges while simultaneously reducing the bending moment and shear force in the tower.

Recently, the elderly population and excessive use of multimedia devices are increasing, which contribute to the growing number of patients with hearing loss. Hearing aids are used as a hearing rehabilitation method for patients with hearing loss and can be classified as air conduction and bone conduction according to the sound transmission pathway. Bone conduction is advantageous over sound transmission as it does not affect the eardrum. Bone conduction systems are divided into BAHA, Bone Bridge and B81 according to the vibration transmission method. BAHA has disadvantages as it can result in skin diseases and has inconveniences, and patients are reluctant to accept Bone Bridge because it has to be implanted into the temporal bone. Due to its location on the skin, B81 can solve these problems; however, this method may reduce transmission efficiency. In this paper, we have proposed a resonance frequency analysis model of a curved beam diaphragm to solve these problems. The proposed method involved a natural frequency equation with derived parameters. An improved efficiency (vibration transmission) was confirmed using the fabricated diaphragm. In the future, the proposed method may be used in various fields.

Little is known about why and how biomechanics govern the hypothesis that three-Lag-Screw (3LS) fixation is a preferred therapeutic technique. A series models of surgical internal-fixation for femoral neck fractures of Pauwells-II will be constructed by an innovative approach of finite element so as to determine the most stable fixation by comparison of their biomechanical performance. Seventeen sets of CT scanned femora were imported onto Mimics extracting 3D models; these specimens were transferred to Geomagic Studio for a simulative osteotomy and kyrtograph; then, they underwent UG to fit simulative solid models; three sorts of internal fixators were expressed virtually by Pro-Engineer. Processed by Hypermesh, all compartments were assembled onto three systems actually as “Dynamic hip screw (DHS), 3LS and DHS+LS”. Eventually, numerical models of Finite Elemental Analysis (FEA) were exported to AnSys for solution. Three models for fixtures of Pauwells-II were established, validated and analyzed with the following findings: Femoral-shaft stress for $c$(3LS) is the least; Internal-fixator stress (MPa) for $a(\mathrm{\text{DHS}})=196.97>b(\mathrm{\text{DHS}}+\mathrm{\text{LS}})=88.37>c(3\mathrm{\text{LS}})=63.81$; Integral stress (MPa) for $a(\mathrm{\text{DHS}})=195.35>b(\mathrm{\text{DHS}}+\mathrm{\text{LS}})=86.72>c(3\mathrm{\text{LS}})=64.60$; displacement of femoral head (mm) for a$(\mathrm{\text{DHS}})=1.068>c(3\mathrm{\text{LS}})=1.010>b$(DHS+LS) = 0.735; displacement of femoral shaft (mm) for $c(3\mathrm{\text{LS}})=0.714>a(\mathrm{\text{DHS}})=0.533>b(\mathrm{\text{DHS+LS}})=0.475$; and displacement of fixators for $c(3\mathrm{\text{LS}})=0.982>a(\mathrm{\text{DHS}})=0.973>b(\mathrm{\text{DHS}}+\mathrm{\text{LS}})=0.706$. Mechanical comparisons for other femoral parks are insignificantly different, and these data can be abstracted as follows: the stress of 3LS-system was checked to be the least, and an interfragmentary displacement of DHS+LS assemblages was assessed to be the least”. A 3LS-system should be recommended to clinically optimize a Pauwells-II facture; if treated by this therapeutic fixation, breakage of fixators or secondary fracture is supposed to occur rarely. The strength of this study is that it was performed by a computer-aided simulation, allowing for design of a preoperative strategy that could provide acute correction and decrease procedure time, without harming to humans or animals.

Hearing loss in people is increasing because of a rise in the usage of wireless audio multimedia devices. Hearing aids are used as representative hearing rehabilitation devices. Bone conduction hearing aids are recommended for problems in the eardrum and middle ear. Bone conduction is classified according to the driving method into two types, electromagnetic and piezoelectric. Electromagnetic bone conduction causes skin disease and aesthetic problems due to transplantation, high power consumption, and external interference. Piezoelectric bone conduction converts electrical energy into mechanical vibrations, and the characteristics change linearly with size. However, the driving force of ear canal insertion of the piezoelectric body is limited because of the ear canal anatomy. In this paper, a piezoelectric actuator with a bridge structure inserted into the ear canal is proposed. The proposed method is that the displacement amplification ratio was derived using the formula of a bridge-type structure, and the displacement and resonance frequency were derived by finite element analysis (FEA) using different variables. The piezoelectric actuator was fabricated on the basis of FEA simulation results and verified through an artificial mastoid for stimulation in the ear canal. It is expected that the proposed piezoelectric actuator can be used in the various fields for sound and precision control.

This study developed a smart sock system using optical fiber technology to measure the toe grip function of individual toes. The system comprised Fiber Bragg grating (FBG) sensors incorporated into a sock garment for measuring maximum toe flexion displacements. Calibration equation of each FBG sensor was determined from 3D motion capture system on 10 female subjects. The validity of the smart sock system was checked by comparing maximum toe flexion displacement against the gold standard of 3D motion capture. The root mean squared error was 0.95 (0.57) cm across 10 toes. The magnitude of toe displacement and error was similar between the left and right feet. In conclusion, the FBG-based smart sock system can successfully measure maximum toe flexion displacements of individual toes simultaneously. This system can be developed to support the evaluation of toe grip function in clinical and field settings.

The state-of-the-art earthquake loss estimation techniques make use of pushover analysis to define the performance of structures under earthquake loading, represented by a demand spectrum whose ordinates reflect the inelastic response. The performance point defined in this way is then used as input to the fragility or loss curves. This rigorous approach represents the earthquake actions by a parameter that is known to have a good correlation with damage and also takes into account the dynamic characteristics of different buildings. However, for many applications, the available data on key input parameters, such as soil conditions and the type and distribution of the exposed building stock, are limited to the extent that the rigorous capacity spectrum approach can become either impractical or unjustified. It is for such case scenarios that a much simpler deformation-based assessment methodology, presented herein, has been developed. The proposed method possesses all the inherent advantages of a displacement-based approach, whilst reducing the required calculations by one or more orders of magnitude when compared to conventional vulnerability assessment procedures.

Displacement based design (DBD) methods are emerging as the latest tool for performance based seismic design. Of the many different DBD procedures proposed in recent years there are few that are developed to a standard suitable for implementation in modern design codes. This paper presents the findings of a study that uses eight different DBD methods to undertake the seismic design of five different case studies. Some significant limitations with the eight methods have been identified through their application to realistic design examples. The study also shows that despite all of the DBD methods using the same set of design parameters, a large variation in design strength is obtained. Finally, through non-linear time history analyses the performance of each method is assessed. The performance assessment indicates that each of the eight DBD methods provide designs that ensure limit states are not exceeded. It is hoped that by presenting the limitations and comparing the required strength and performance of the methods, developments will be made that will enable designers to undertake DBD with ease and confidence.

Seismic assessment of existing reinforced concrete frame and shear wall buildings is discussed. Building on an earlier preliminary assessment procedure incorporating aspects of capacity design into a systems approach for assessment, suggestions are made towards a displacement-based, rather than forced-based, approach to determining available seismic capacity. Based on results from recent experimental programs, procedures are proposed for assessing member strength including column and beam-column joint shear-strength, that result in less conservative estimates of performance than would result from application of existing code rules.

A summary of dynamic measurements are presented that illustrate relations between linear seismic demand and true nonlinear response of unreinforced masonry buildings with flexible diaphragms and rocking piers subjected to a series of simulated earthquake motions.

The attenuation of the maximum shear wave for strong ground displacements in large earthquakes (5.4 < M_w < 7.2) in California was studied from a seismological viewpoint. Smooth regression curves of attenuation were statistically fitted to measurements made personally on each seismogram. The curves were computed for two different geological classifications of the recording location (rock or soil), and two different fault mechanisms of the seismic source (strike-slip or reverse-fault). The sample consisted of eight strike-slip and four reverse-fault mechanism earthquakes with 237 soil and 92 rock peak ground displacement measurements.

The peak ground-motion displacements were measured from the S body-wave portion of the seismograms (frequencies between 0.2 and 1 Hz) after discrimination of the seismic wave types. The peak displacement from any surface wave train was not considered in this analysis. An attenuation distance H_slip was used as the distance from the recording station to the location on the fault plane of largest slip. Two sub-samples were formed consisting of the transverse (SH) and vertical (SV) measurements.

The set of ground-displacement attenuation curves predict greater amplitudes at sites classified as soil sites compared to rock sites, and for SH versus SV motion for both types of seismic source mechanisms.

Evaluating the seismic stability of a rock slope typically involves searching for the minimum value of calculated safety factors (SF) for each supposed sliding block. Because only the transient equilibrium is evaluated, the likelihood of any slope failure can be deemed negligible if all the calculated SFs are greater than unity. However, even if some of the calculated SF are less than unity, it cannot be assumed that the slope will collapse. Recently, in the wake of extremely large earthquakes in Japan, the design earthquake standards for nuclear power plants (NPP) have been extended. After the experience of the 2011 off the Pacific coast of Tohoku Earthquake, the designer is expected to consider beyond design basis earthquakes to determine whether more can reasonably be done to reduce the potential for damage, especially where major consequences may ensue [IAEA (2011). IAEA international fact finding expert mission of the Fukushima dai-ichi NPP accident following the Great East Japan Earthquake and Tsunami, Mission report, IAEA]. With this in mind, the method employed to evaluate the seismic performance of the slope surrounding an NPP needs to be capable of doing more than determining the likelihood of failure: it must also consider the process toward failure in the event of an earthquake beyond the design basis. In this paper, a new evaluation flow which considers the failure process is proposed to evaluate the seismic performance of slopes surrounding an NPP. This is followed by confirming the validity of the concepts in the proposed flow chart by re-evaluating centrifuge tests in past literature and the numerical simulations designed for those tests.

While recent research pays attention to the sociabilities of emplacement — defined as the interactions through which migrants form social relations upon settlement — to moderate the shortcomings of integration theory and the ethnic lens (Glick Schiller and Çağlar 2016), researchers have largely ignored the sociabilities that happen on digital platforms. This chapter makes sense of the digital sociabilities of emplacement based on a virtual ethnographic study conducted on Facebook groups for Vietnamese migrants in Taiwan. This chapter focuses on the digital sociabilities of low-skilled and mid-skilled Vietnamese labour migrants who face tremendous forms of displacement such as long work hours, isolated employer-provided living arrangements, a lack of language skills, and the risk of exploitation and discrimination. This chapter focuses on the sociabilities of transregional migrants whom I define as migrants who develop and maintain multi-faceted connections linking multiple places, spaces, and scales. In this chapter, I argue that by forging social relations via digital platforms, transregional migrants engage in the processes of building and rebuilding networks of connection within the constraints and opportunities of their specific locales and predicament of displacement. This chapter contributes to understanding how people deal with the growing disparities and displacements of global capitalism by addressing how transregional migrants use digital technologies as multiscalar tools to overcome precariousness and displacement.

The boiler's steam pipes are a vital component of the steam-water piping system. As these pipes usually work under abnormal conditions due to deformations caused by the environment's high temperature and pressure, they must be effectively monitored. The digital image correlation method has increasingly been used for thermal deformation in recent years. Compared to traditional gauges, this method is both easier to implement and less costly. Analysis software processes the images and calculates strain automatically. Based on this method, an algorithm for strain computing is proposed, and a model for pipe deformation is presented. Required measurement steps are explained and the experimental results are reported. The used algorithm is explained and its reliability is discussed. Experimental results show that the method is both feasible and reliable.

This paper describes the analysis of the calibration procedure of a computational optical system applied in the dimensional monitoring of the 25^th of April suspension bridge (P25A) in Lisbon (Portugal). The analysis includes the displacement optical measurement approach, the calibration method, the reference standard prototype and the experimental setup. The evaluation of the measurement uncertainty is described, including input measurement uncertainty contributions related to the experimental design and the use of Monte Carlo numerical simulation as tool for determination of the measurement uncertainty related to the calibration test, as well as a sensitivity analysis to identify the major sources of uncertainty. Conclusions are drawn about the suitability of the calibration method and reference standard prototype.