Search Results (6)

Persistent localization is a critical requirement for autonomous underwater vehicles (AUVs) engaged in long-term missions. Conventional dead-reckoning (DR) methods for estimating the position and orientation of AUVs often suffer from drift, necessitating additional information to correct accumulating errors. In this paper, we propose a visual artificial landmarks-based simultaneous localization and mapping (SLAM) system for AUVs. This system utilizes two types of underwater artificial landmarks that are observed using forward and downward-looking cameras. The information obtained from these detected landmarks, along with incremental DR estimates, is integrated within a framework based on the extended Kalman filter (EKF) SLAM approach, allowing for the recursive estimation of both the robot and the landmark states. We implemented the proposed visual SLAM method using our yShark II AUV and conducted experiments in an engineering basin to validate its effectiveness. A ceiling vision-based reference pose acquisition system was installed, facilitating a comparison between the pose estimation results obtained from DR and those derived from the SLAM method. Full article

Corneal neovascularization is a significant cause of vision loss, often resulting in corneal clouding and chronic inflammation. Shark cartilage is widely recognized as a significant natural source of anti-angiogenic compounds. Our previous studies have shown that a polypeptide from white-spotted catshark (Chiloscyllium plagiosum Bonnet) has the potential to inhibit the angiogenesis of breast tumors. This study applied this peptide (SAIF) to a corneal alkali injury model to assess its effect on corneal neovascularization. Results revealed that SAIF inhibits endothelial cell proliferation, migration, and tube formation. SAIF inhibited VEGF-induced angiogenesis in the matrigel plug. Using the corneal alkali injury model, SAIF significantly inhibited corneal vascular neovascularization in mice. We found that SAIF not only significantly inhibited the upregulation of pro-angiogenic factors such as VEGF, bFGF, and PDGF expression induced by alkali injury, but also promoted the expression of anti-angiogenesis factor PEDF. Moreover, we also analyzed the MMPs and TIMPs involved in extracellular matrix (ECM) remodeling, angiogenesis, and lymphangiogenesis. We found that SAIF treatment inhibited the expression of pro-angiogenic factors like MMP1, MMP2, MMP3, MMP9, MMP13, and MMP14, and promoted the expression of anti-angiogenesis factors such as MMP7, TIMP1, TIMP2, and TIMP3. In conclusion, SAIF acts as an anti-angiogenic factor to inhibit the proliferation, migration, and tube formation of endothelial cells, inhibit pro-angiogenic factors, promote anti-angiogenic factors, and regulate the expression of MMPs, ultimately inhibiting corneal neovascularization. Full article

The recent progress in deep learning has given rise to a non-invasive and effective approach for animal biometrics. These modern techniques allow researchers to track animal individuals on a large-scale image database. Typical approaches are suited to a closed-set recognition problem, which is to identify images of known objects only. However, such approaches are not scalable because they mis-classify images of unknown objects. To recognize the images of unknown objects as ‘unknown’, a framework should be able to deal with the open set recognition scenario. This paper proposes a fully automatic, vision-based identification framework capable of recognizing shark individuals including those that are unknown. The framework first detects and extracts the shark from the original image. After that, we develop a deep network to transform the extracted image to an embedding vector in latent space. The proposed network consists of the Visual Geometry Group-UNet (VGG-UNet) and a modified Visual Geometry Group-16 (VGG-16) network. The VGG-UNet is utilized to detect shark bodies, and the modified VGG-16 is used to learn embeddings of shark individuals. For the recognition task, our framework learns a decision boundary using a one-class support vector machine (OSVM) for each shark included in the training phase using a few embedding vectors belonging to them, then it determines whether a new shark image is recognized as belonging to a known shark individual. Our proposed network can recognize shark individuals with high accuracy and can effectively deal with the open set recognition problem with shark images. Full article

Between the years 2008 and 2013, six annual research expeditions were carried out at Dyer Island (Gansbaai, South Africa) to study the surface behaviour of white sharks in the presence of two passive prey: tuna bait and a seal-shaped decoy. Sightings were performed from a commercial cage-diving boat over 247 h; 250 different white sharks, with a mean total length (TL) of 308 cm, were observed. Of these, 166 performed at least one or more interactions, for a total of 240 interactions with bait and the seal-shaped decoy. In Gansbaai, there is a population of transient white sharks consisting mainly of immature specimens throughout the year. Both mature and immature sharks preferred to prey on the seal-shaped decoy, probably due to the dietary shift that occurs in white sharks whose TL varies between 200 cm and 340 cm. As it is widely confirmed that white sharks change their diet from a predominantly piscivorous juvenile diet to a mature marine mammalian diet, it is possible that Gansbaai may be a hunting training area and that sharks show a discriminate food choice, a strategy that was adopted by the majority of specimens thanks to their ability to visualize energetically richer prey, after having been attracted by the odorous source represented by the tuna bait. Full article

To ascertain how scalloped hammerhead sharks make nightly migrations to their feeding grounds as many as 20 km from their daytime abode, a seamount, a sensor was developed that measured irradiance intensity within the spectral range and sensitivity of the vision of the species. Could the sharks guide their movements by sensing the polarity of irradiation energy radiated from the sun or moon that penetrated into the oceanic depths? Two sensory receptors, cones and rods, are present in the retina of sharks to enable them to see both during daytime and nighttime. The peak sensitivity of the cones is red-shifted due to the presence of these wavelengths during the former period, while their response is linear under the range of the high light levels also present at this time; the peak sensitivity of rods is blue-shifted due to the presence of these wavelengths during dawn, dusk, and nighttime and is linear over the complementary range of low light levels. Spectral response curves for these two receptors were determined for sharks, and an attempt was made to match those of the sensors to the shark’s wavelength perception. The first sensor was matched to the photopic range using a photocell covered with a red-shifted gel filter; the second was matched to the scotopic range using a blue-shifted gel filter. Full article

It is largely assumed that Islamic microfinance institutions (IMFIs) deal with family empowerment instead of women’s empowerment. However, women are the main beneficiaries of Baitul Maal Wat Tamwil (BMT), Indonesia’s first IMFIs. This paper aims to explore the origins, the initiators, and the visions of BMTs and the extent to which they intersect with women’s empowerment. Employing a qualitative approach, this study selected four BMTs in Yogyakarta as a case study. It found that four critical groups that have a significant role in the development of Indonesian BMTs: ICMI (Association of Indonesian Muslim Intellectual), Islamic mass organizations, NGOs, and local governments. The issues of loan sharks and poverty alleviation were the primary factors driving the inception of BMTs. Despite women being crucial clients, none of the studied BMTs explicitly invoked women’s empowerment in their organizational vision. To conclude, the BMTs’ preference for women is not based on an understanding of gender inequality, but rather motivated by pragmatic business considerations, particularly the self-sustainability paradigm that underpins their practices. Full article