Broad attention uncovers benefits of stimulus uniformity in visual crowding

Crowding is the interference by surrounding objects (flankers) with target perception. Low target-flanker similarity usually yields weaker crowding than high similarity (‘similarity rule’) with less interference, e.g., by opposite- than same-contrast polarity flankers. The advantage of low target-flanker similarity has typically been shown with attentional selection of a single target object. Here, we investigated the validity of the similarity rule when broadening attention to multiple objects. In three experiments, we measured identification for crowded letters (Experiment 1), tumbling Ts (Experiment 2), and tilted lines (Experiment 3). Stimuli consisted of three items that were uniform or alternating in contrast polarity and were briefly presented at ten degrees eccentricity. Observers reported all items (full report) or only the left, central, or right item (single-item report). In Experiments 1 and 2, consistent with the similarity rule, single central item performance was superior with opposite- compared to same-contrast polarity flankers. With full report, the similarity rule was inverted: performance was better for uniform compared to alternating stimuli. In Experiment 3, contrast polarity did not affect performance. We demonstrated a reversal of the similarity rule under broadened attention, suggesting that stimulus uniformity benefits crowded object recognition when intentionally directing attention towards all stimulus elements. We propose that key properties of crowding have only limited validity as they may require a-priori differentiation of target and context.

Changes in the Dynamic Characteristics of a Small-Scale Gymnasium Model Due to Simulated Earthquake Damage

In this study, the authors used shake-table tests to assess the modal parameters of a small-scale gymnasium model with simulated damage, the feasibility of estimating the damage to large-span building structures was studied. In Japan, large-span structures, such as gymnasiums, are expected to be used as evacuation shelters when a natural disaster occurs. As the shelter itself may be damaged in case of an earthquake, it is critical to determine whether damage has occurred, where it occurred, and how serious it is, before the shelter is used. The small-scale gymnasium was designed based on the similarity rule. Observed earthquake ground motions scaled to aftershock levels were applied to the model. The natural frequencies and mode shapes were obtained from the measured response accelerations. To study the influence of structural damage on the modal parameters, a gymnasium model with simulated damage was also tested. The results indicate that the modal parameters, e.g., natural frequencies and mode shapes, can be obtained from the response accelerations, and the damage patterns can be estimated from the changes in these modal parameters.

Influence of Structural Interface Opening of Bolted Joints Under Eccentric Load

It is important to evaluate the safety of bolted joint under a load eccentric to a bolt axis. We examined tapped thread joints, with which a clamped plate is tightened with bolts to a base body, by applying eccentric loads to the bolts. The structural interface opening between the clamped plate and base body occurs due to the eccentric load based on the principle of leverage. During the growth of the interface opening, nonlinearity noticeably appears on the tensional and bending components of bolt stress, and these stress components become larger than expected in an early phase before a fatal bolt pull-out occurs. However, an evaluation method taking into account nonlinearity has not been investigated. We propose a normalized-bolt-stress evaluation method for tapped thread joints that takes into account the effect of the nonlinearity of bolt stress during interface opening. We conducted numerical calculations, experiments, and finite element analyses to quantitatively validate the stress under the following conditions: (i) tapped thread joints with the clamped plate thinner than the bolt diameter and (ii) load eccentric to the bolt axis. We confirmed that the bolt preload and lever ratio should be fixed at an initial phase, in which has no interface openings for the appropriate normalization. By using the normalized-bolt-stress evaluation method, strength evaluation becomes easily applicable to layout changes of bolted joints as a similarity rule.

Ship Maneuvering Prediction Using Grey Box Framework via Adaptive RM-SVM with Minor Rudder

A grey box framework is applied to model ship maneuvering by using a reference model (RM) and a support vector machine (SVM) (RM-SVM). First, the nonlinear characteristics of the target ship are determined using the RM and the similarity rule. Then, the linear SVM adaptively fits the errors between acceleration variables of RM and target ship. Finally, the accelerations of the target ship are predicted using RM and linear SVM. The parameters of the RM are known and conveniently acquired, thus avoiding the modeling process. The SVM has the advantages of fast training, quick simulation, and no overfitting. Testing and validation are conducted using the ship model test data. The test case reveals the practicability of the RF-SVM based modeling method, while the validation cases confirm the generalization ability of the grey box framework.