Algorithm for Compression Design Allowable Determination of Composite Laminates with Initial Delaminations

With the increasing demands for detailed design of composite aircraft structures, the method of covering all damages with low design allowables cannot meet the current requirements for aircraft structure design. Herein, this paper proposes a novel algorithm for design allowable determination of composite laminates by combining the damage distribution with damage factor model of design allowable, so as to provide different structures with more accurate design allowables based on their initial damages. For the composite laminates with initial delaminations, a model describing the effect of delamination size and depth position on the compression design allowable is developed and the compression design allowable of different aircraft structures are individually determined by employing abundant initial delamination statistics. Compared with the design allowable offered by the single-point method, the design allowable based on the initial damage can be increased by at least 5% to 20%, greatly improving the economic benefits of the aircraft structures and providing an important support for the damage tolerance design of the composite structures.

COMPREHENSIVE EVALUATION OF FACTORS LEADING TO CLASS III SUBDIVISION MALOCCLUSION USING 3-D CBCT

Introduction:Several studies have been conducted to assess skeletal and dental asymmetry on Class II subdivision cases but no studies have yet been published to assess such asymmetries for patients with Class III subdivision malocclusion. The purpose of the study was to assess the maxilla-mandibular dimensional and positional asymmetry along with asymmetry at glenoid fossa level and to find out true dental asymmetry at molar and canine level in class III subdivision malocclusion. Materials and Methods: A split mouth prospective study was conducted on Angles Class III subdivision malocclusions (n=15) and CBCT scans were analyzed with 3-D Dolphin software. 3-D and 2-D measurements were recorded to assess asymmetry between class I and class III sides. 2-D measurements were recorded to assess the position of glenoid fossa, joint spaces and condyle dimension, position and their angulation. Results: Statistically significant differences were found in glenoid fossa depth, position of the maxilla, mandible, as well as in gonial angle. Statistically significant dental differences were also found for the position of the mandibular first molars and canines along with total asymmetry (combined skeletal and dental) in maxilla and mandible. Conclusions: The components contributing to Class III subdivision malocclusion were multifactorial involving glenoid fossa asymmetry, positional asymmetry in maxilla and mandible. Mandibular dimensions were more on class III side but it was not statistically significant. True dental asymmetry was also foundin mandible along with total asymmetry in maxilla and mandible.

Experimental Scours by Impinging Twin-Propeller Jets at Quay Wall

Experiments were conducted to investigate the seabed scour holes due to the interaction between the twin-propeller jet and quay wall. Vertical quay wall was modelled by using a polyvinyl chloride (PVC) plastic plate in a water tank. The relationship between the positions of the propeller and the vertical quay wall was designed according to the actual working conditions of a ship entering and leaving a port. Propeller-to-wall distance and rotational speed were changed to observe the various scour conditions. The scour depth was measured by using an Acoustic Doppler Velocimeter (ADV). Primary scour hole was found within the jet downstream and secondary scour hole occurred beneath of the propeller. Third scour hole was found close to the quay wall due to horseshoe vortices. The maximum scour position of this third scour hole was found at the jet centre near the quay wall. Temporal formation of scour holes can be divided into three stages: axial scour formation, obstructed scour expansion and equilibrium stages. The quantitative relationships for six characteristic parameters of the scour pit were established including the maximum scour depth (εmax,q), maximum scour depth position (Xm,q), maximum scour width (Wm,q), length of main scour pit (XS,q), maximum deposition height (ZD,q), and location of maximum deposition height (XD,q).

DUAL MODALITY TRAN-ADMITTANCE MAMMOGRAPHY AND ULTRASOUND REFLECTION TO IMPROVE ACCURACY OF BREAST CANCER DETECTION

Cancer and breast tissue have a very high electrical impedance ratio, so imaging based on impedance can produce high contrast. It is very useful for the early detection of breast cancer. Trans-admittance mammography (TAM) is a modality to detect breast cancer based on impedance. The weakness of TAM is that it can only produce a projection image so that the volume and ratio of cancer to breast tissue cannot be obtained at once. The ratio of anomaly and volume is very important to be determined properly because it is related to the stage and type of cancer. TAM shortcomings can be overcome if anomalous volume information is known precisely. The ultrasound reflection modality can produce information about an anomaly depth and volume correctly. Combining TAM and ultrasound reflection data is expected to provide promising results. The study was conducted to prove the hypothesis by creating a breast phantom composed of gelatin, agar, graphite, glycerol, and distilled water to represent the electrical and acoustic physical properties of cancer and breast tissue. The results showed that the TAM data was only able to produce information about transverse position accurately, while the depth was less accurate. Acoustic devices can produce transverse position information, depth, and volume precisely. The dual-modality of TAM and ultrasound reflection can produce information about the depth position, volume, and the ratio anomaly to reference conductivity accurately.

Noise Sensitivities for an Atom Shuttled by a Moving Optical Lattice via Shortcuts to Adiabaticity

We find the noise sensitivities (i.e., the quadratic terms of the energy with respect to the perturbation of the noise) of a particle shuttled by an optical lattice that moves according to a shortcut-to-adiabaticity transport protocol. Noises affecting different optical lattice parameters, trap depth, position, and lattice periodicity, are considered. We find generic expressions of the sensitivities for arbitrary noise spectra but focus on the white-noise limit as a basic reference, and on Ornstein–Uhlenbeck noise to account for the effect of non-zero correlation times.

Human Depth Sensitivity Is Affected by Object Plausibility

Using behavioral and fMRI paradigms, we asked how the physical plausibility of complex 3-D objects, as defined by the object's congruence with 3-D Euclidean geometry, affects behavioral thresholds and neural responses to depth information. Stimuli were disparity-defined geometric objects rendered as random dot stereograms, presented in plausible and implausible variations. In the behavior experiment, observers were asked to complete (1) a noise-based depth task that involved judging the depth position of a target embedded in noise and (2) a fine depth judgment task that involved discriminating the nearer of two consecutively presented targets. Interestingly, results indicated greater behavioral sensitivities of depth judgments for implausible versus plausible objects across both tasks. In the fMRI experiment, we measured fMRI responses concurrently with behavioral depth responses. Although univariate responses for depth judgments were largely similar across cortex regardless of object plausibility, multivariate representations for plausible and implausible objects were notably distinguishable along depth-relevant intermediate regions V3 and V3A, in addition to object-relevant LOC. Our data indicate significant modulations of both behavioral judgments of and neural responses to depth by object context. We conjecture that disparity mechanisms interact dynamically with the object recognition problem in the visual system such that disparity computations are adjusted based on object familiarity.

Velocity-independent Marchenko focusing in time- and depth-imaging domains for media with mild lateral heterogeneity

The Marchenko method retrieves Green’s functions between the acquisition surface and any arbitrary point in the medium. The process generally involves solving an inversion starting with an initial focusing function, e.g., a direct-wave Green’s function from the desired subsurface position, typically obtained using an approximate velocity model. We have formulated the Marchenko method in the time-imaging domain. In that domain, we recognize that the traveltime of the direct-wave Green’s function is related to the Cheop’s traveltime pyramid commonly used in time-domain processing, which in turn can be readily obtained from the local slopes of the common-midpoint gathers. This observation allows us to substitute the velocity-model-based initial focusing operator with that from a data-driven slope estimation process. Moreover, we found that working in the time-imaging domain allows for the specification of the desired subsurface position in terms of vertical time, which is connected to the Cartesian depth position via the time-to-depth conversion. Our results suggest that the prior velocity model is only required when specifying the position in depth, but this requirement can be circumvented by making use of the time-imaging domain within its usual assumptions (e.g., mild lateral heterogeneity). Provided that those assumptions are satisfied, the estimated Green’s functions from the proposed method have comparable quality to those obtained with the knowledge of a prior velocity model.