Blur Reduction in Ultrasonic Images Using Pseudo Three-Dimensional Wiener Filtering

The ability to quantitatively image material anomalies with ultrasonic methods is severely restricted by the axial and lateral resolution of the interrogating transducer. Axial resolution is controlled by the pulse duration of the transducer with shorter pulse durations yielding better axial resolution. Lateral resolution is controlled by the width of the interrogating beam with narrower beams providing better lateral resolutio

Impact-Induced Delaminations in Thermoset and Thermoplastic Composites

Laminated fiber-reinforced composites are engineering materials with many desirable properties including high stiffness and strength. However, the lack of fiber reinforcement in the through-thickness direction makes composite laminates vulnerable to foreign object impact loading. Transverse impact loading can lead to a variety of damages including matrix cracking, delamination and fiber breakage. Delaminations can reduce the strength of a laminate, especially the compressive strength after impact. Impact loading typically causes multiple delaminations that vary in size and shape by depth location. The fracture behavior of impact damages has been a topic of extensive research [1]. Recently significant advances have been made in the area of nondestructive evaluation (NDE) of impact damages in composites. For example, ultrasound is used to map out the details of impact-induced delaminations with ply-by-ply resolution [2].</p

Imaging of Impact Damage in Composite Materials

Conventional ultrasonic C-scan images are generated from information acquired within “gates” placed at specific temporal locations on low-pass filtered and rectified versions of A-scans. Placing the gates at temporal locations which correspond with interfaces allows the integrity of the interfaces to be examined. However, if the interfaces are closely spaced, as is the case for quasi-isotropic graphite/epoxy composites, the information from upper layers is blurred into the layers below because of the finite time duration of the ultrasonic pulse. This creates a low signal-to-background-level ratio, which causes blurring at and below the first interface

Correlation of Ultrasonic Imaging and Destructive Analyses of Low Energy Impact Events

Some of the most critical flaws encountered during the service life of a composite component can result from impact damage due to foreign objects (FOD). Impact damage can produce significant degradation of the material’s structural integrity. Destructive sectioning [1] or de-plying [2,3] of impact damaged laminates has proven that damage is manifested in the form of interlaminar delaminations, each of different size, shape and ply interface orientation through the thickness. Unfortunately, the extent of the delamination damage, especially at low level impact sites, may not be visually identified from surface features. The seriousness of this problem has led to much work in both the nondestructive evaluation and mechanics communities to characterize and assess the effects of such damage

Oblivious routing for LC permutations on hypercubes

We propose an oblivious algorithm to route linear-complement (LC) permutations on hypercubes in circuit switched and wormhole routing. The algorithm guarantees that N independent paths can be set up simultaneously for any LC permutation with only a comparison of two bits in one routing step for any path. An LC permutation is determined by a transformation matrix T and a constant modifier C. For all the LC permutations with the same transformation matrix T (we call them a type of permutations), an algorithm is executed to find an ordered sequence of dimensions without knowing a particular permutation. When the sequence of dimensions is used in the routing process for all the packets of a permutation of this type, a comparison of two bits is carried out in each routing step in the packet transmission process. It is guaranteed that no contention will occur between any two paths on the use of the dimensional links, thus N independent paths can be set up simultaneously for the N packets of an LC permutation. Time complexity of the algorithm for finding an ordered sequence for the use of the n dimensions is O(n3) for any type of LC permutations (rather than one particular LC permutation), and it can be carried out off-line. The routing process itself is distributed, and oblivious.link_to_subscribed_fulltex

Cardiovascular Efficacy and Safety of Bococizumab in High-Risk Patients

Bococizumab is a humanized monoclonal antibody that inhibits proprotein convertase subtilisin- kexin type 9 (PCSK9) and reduces levels of low-density lipoprotein (LDL) cholesterol. We sought to evaluate the efficacy of bococizumab in patients at high cardiovascular risk. METHODS In two parallel, multinational trials with different entry criteria for LDL cholesterol levels, we randomly assigned the 27,438 patients in the combined trials to receive bococizumab (at a dose of 150 mg) subcutaneously every 2 weeks or placebo. The primary end point was nonfatal myocardial infarction, nonfatal stroke, hospitalization for unstable angina requiring urgent revascularization, or cardiovascular death; 93% of the patients were receiving statin therapy at baseline. The trials were stopped early after the sponsor elected to discontinue the development of bococizumab owing in part to the development of high rates of antidrug antibodies, as seen in data from other studies in the program. The median follow-up was 10 months. RESULTS At 14 weeks, patients in the combined trials had a mean change from baseline in LDL cholesterol levels of -56.0% in the bococizumab group and +2.9% in the placebo group, for a between-group difference of -59.0 percentage points (P<0.001) and a median reduction from baseline of 64.2% (P<0.001). In the lower-risk, shorter-duration trial (in which the patients had a baseline LDL cholesterol level of ≥70 mg per deciliter [1.8 mmol per liter] and the median follow-up was 7 months), major cardiovascular events occurred in 173 patients each in the bococizumab group and the placebo group (hazard ratio, 0.99; 95% confidence interval [CI], 0.80 to 1.22; P = 0.94). In the higher-risk, longer-duration trial (in which the patients had a baseline LDL cholesterol level of ≥100 mg per deciliter [2.6 mmol per liter] and the median follow-up was 12 months), major cardiovascular events occurred in 179 and 224 patients, respectively (hazard ratio, 0.79; 95% CI, 0.65 to 0.97; P = 0.02). The hazard ratio for the primary end point in the combined trials was 0.88 (95% CI, 0.76 to 1.02; P = 0.08). Injection-site reactions were more common in the bococizumab group than in the placebo group (10.4% vs. 1.3%, P<0.001). CONCLUSIONS In two randomized trials comparing the PCSK9 inhibitor bococizumab with placebo, bococizumab had no benefit with respect to major adverse cardiovascular events in the trial involving lower-risk patients but did have a significant benefit in the trial involving higher-risk patients