Entrance Depth Research Articles

The Effects of Depth and Habitats on Bycatch Distribution in Deployed Fish Traps in Bidong Archipelago, Terengganu – Peninsular Malaysia

Graphical Abstract Highlight Research 1. Fish traps at 20 m depth captured the highest species diversity, while 10 m had the most bycatch abundance. 2. Habitat type strongly influenced bycatch composition and species richness, with differences across the study stations. 3. Artisanal fish traps captured a wide range of species, indicating non-selectivity in fishing. 4. Bycatch composition varied with depth, with demersal species being predominant at greater depths. 5. The study recommends management strategies like time-release mechanisms to minimize the ecological impact of fish traps. AbstractIn many marine ecosystems, the fish population has been correlated to bycatch related activities, the most frequently fisheries activities in Malaysia, while the relative importance of other factors such as the depth of artisanal fish trap remains understudied. We investigate whether the bycatch distribution would be affected by deployment of artisanal fish trap at different depths, placed at extensively studied marine educational university station, the Bidong Island, East Coast of Peninsular Malaysia, Terengganu. The traditional artisanal fish trap with a dimension of 1.52 m x 0.92 m x 0.92 m with the wooden frame and the oval shape funnel with a diameter of 25 cm x 6 cm and 25 cm of entrance depth were used for sample collection. The results show that there are six families, six genera and seven species of fish were successfully captured with a 20 m depth captured more fish species compared to others (i.e., 10 m and 15 m depth). The findings of this study provide evidence of the relationship of fish trap depths and fish distribution in the wild. This information could be useful for fishermen for further deployment of their fish trap within the sampling areas in the future.

Analysis of Resonance Efficiency According to Length and Entrance Depth of Channel Resonance Part of Multi-Resonance Wave Energy Converter

Multi-resonance wave energy converter can generate efficient power generation by complexly utilizing the resonance phenomenon of waves even when waves propagate normally. As the wave is amplified by resonance, the power generation efficiency of the multi-resonance wave energy converter increases, and the shape of the resonance part needs to be optimized to maximize power generation efficiency. The multi-resonance wave energy converter amplifies waves in the seiche resonance part and the channel resonance part. In this study, CFD numerical experiments were performed under various conditions such as the length and location of the channel resonance part to analyze the sensitivity for each condition and derve the optimal shape of the channel resonance part.

The impact of DNA double-strand break repair pathways throughout the carbon ion spread-out Bragg peak beam.

Following carbon ion beam irradiation in mammalian cells, such as used in carbon ion radiotherapy (CIRT), it has been suggested that the balance between whether nonhomologous end joining (NHEJ) or homologous recombination (HR) is utilized depends on the DNA double-strand break (DSB) complexity. Here, we quantified DSB distribution and identified the importance of each DSB repair pathway at increasing depths within the carbon ion spread-out Bragg peak (SOBP) beam range. Chinese hamster ovary (CHO) cell lines were irradiated in a single biological system capable of incorporating the full carbon ion SOBP beam range. Cytotoxicity and DSB distribution/repair kinetics were examined at increasing beam depths using cell survival as an endpoint and γ-H2AX as a surrogate marker for DSBs. We observed that proximal SOBP had the highest number of total foci/cell and lowest survival, while distal SOBP had the most dense tracks. Both NHEJ- and HR-deficient CHO cells portrayed an increase in radiosensitivity throughout the full carbon beam range, although NHEJ-deficient cells were the most radiosensitive cell line from beam entrance up to proximal SOBP and demonstrated a dose-dependent decrease in ability to repair DSBs. In contrast, HR-deficient cells had the greatest ratio of survival fraction at entrance depth to the lowest survival fraction within the SOBP and demonstrated a linear energy transfer (LET)-dependent decrease in ability to repair DSBs. Collectively, our results provide insight into treatment planning and potential targets to inhibit, as HR was a more beneficial pathway to inhibit than NHEJ to enhance the cell killing effect of CIRT in targeted tumor cells within the SOBP while maintaining limited unwanted damage to surrounding healthy cells.

EVRİŞİMLİ SİNİR AĞI TABANLI DERİNLİK HARİTASI İYİLEŞTİRME

Bir ortamın derinlik bilgisi üç boyutlu yeniden oluşturma, otonom sistemler gibi derinlik bilgisine ihtiyaç duyulan birçok uygulamada yoğun olarak kullanılmaktadır. Stereo görüntü çiftleri kullanılarak derinlik bilgisi elde edilmesi, uzun yıllardır öne çıkan çalışma konuları arasında yer almaktadır. Son yıllarda derin öğrenme alanındaki gelişmeler, stereo görüntüler kullanılarak derinlik elde edilmesi alanında yapılan çalışmaları da etkilemiştir. Son dönemde, derin öğrenme tabanlı stereo eşleştirme alanındaki çalışmalar daha çok derinlik (eşitsizlik) haritalarının elde edilmesi ve düzeltilmesi alanında yoğunlaşmaktadır. Derin öğrenme tabanlı derinlik haritası düzeltme işlemlerinde eşleşme maliyetleri üzerinden yapılan düzeltme işlemleri daha başarılı sonuçlar üretilmesini sağlamıştır. Fakat eşleşme maliyetlerine doğrudan ulaşmak her zaman mümkün olmamaktadır. ZED ve Intel RealSense gibi hazır sistemler tarafından üretilen derinlik haritaları son kullanıcıya sunulmaktadır. Çalışmada sadece sol görüntü ve derinlik haritası aracılığıyla düzeltme işlemi yapan bir ağ yapısı önerilmiştir. Önerilen ağ, KITTI 2012 ve KITTI 2015 veri kümeleri üzerinde test edilmiştir. Deneysel çalışmalar sonucunda olarak giriş derinlik haritalarının doğruluğunun arttırılması için önerilen ağ yapısının kullanılabileceği nicel ve nitel sonuçlar ile gösterilmiştir.

Numerical Investigation of Geometrical Design Effect on the Submerged Inlet Aerodynamics Characteristics

In the present study, turbulent flow at submerged inlets is numerically studied. Five different geometries including the standard inlet developed by National Advisory Committee for Aeronautics (NACA), divergent inlet, parallel inlet and two new proposed geometries are compared. The effects of the boundary layer thickness ratio (0.31, 0.8 and 2.56) defined as the ratio between the boundary layer thickness (\( \delta \)) and the entrance depth (d) and velocity ratio defined as the ratio between the flow velocity at the duct entrance and the free stream (0.2–1.6) on their performance are further investigated. Moreover, the \( \,K - \omega \; \) model is used to simulate the three-dimensional, incompressible and turbulent flow of interest. NACA inlet is validated with experimental data. Results showed that in all studied cases, increasing the boundary layer thickness has a negative effect on the Ram recovery ratio (or efficiency); however, the effect of the velocity ratio on the Ram recovery ratio was different with an initial increase followed by a decrease in the efficiency. It is shown that our two proposed inlets present the same efficiency as the NACA inlet, while the efficiency for the divergent and parallel inlets was lower. Interestingly, the proposed inlets show a lower drag force compared to the NACA inlet at the high velocity ratios.

Response of a barrier estuary to climate change and river regulation using attractor analysis: Snowy River estuary, Australia

AbstractThe evolution of the entrance channel of the Snowy River estuary in response to river regulation and climate change is predicted. The predictions are made in terms of the physical attractors that define possible long‐term states of the estuary entrance condition. The classification of these attractors shows the dependence of the entrance stability on the catchment inflows and the present entrance depth. The Snowy River estuary in south‐eastern Australia is a barrier estuary with an unstable entrance that tends to closure. The classification from the attractor map shows that the estuary entrance has changed from predominantly stable to a predominantly unstable state attributable to diversion of water from the upper catchment. The introduction of a series of environmental flow regimes, commencing in 2002, has returned 8% rising to 21% of the mean annual natural flow, but this study shows that the releases provide limited improvement in entrance stability. Additionally, the predicted effects of climate change for this region include increased mean sea level (MSL), decreased annual rainfall, and increased incidence of storms. These changes will decrease stability, primarily through the rise in MSL. The rise in sea level will increase the plan area of the tidal basin, increasing the tidal prism, and hence drawing in more marine sand. The application to the Snowy River estuary provides a proof of concept of the attractor classification to support estuary management.

Simulative research on reverse current in magnetically insulated coaxial diode

The reverse current tends to occur in the transition region of the guiding magnetic field in a magnetically insulated coaxial diode (MICD). Influence of the guiding magnetic field on characteristics of the MICD especially on the reverse current is studied by the particle-in-cell (PIC) simulation in this paper. The reverse current is confirmed to be irrelevant with the guiding magnetic field strength. However, the reverse current is clarified quantitatively to depend on the electric and magnetic field distribution in the upstream of the cathode tip. As the MICD has been widely employed in microwave tubes, a simple approach to suppress the reverse current on the premise of little change of the original diode is valuable and thus proposed. The optimum matching point between the cathode and the magnetic field is selected in consideration of the entrance depth tolerance, the diode impedance discrepancy and the reverse current coefficient.

Aerodynamic and aeroacoustic analyses of a submerged air inlet in a low-Mach-number flow

Computational aerodynamic and aeroacoustic analyses of a submerged air inlet are performed at a low Mach number. A hybrid method is used, in which the flow in the vicinity of the inlet is solved through detached eddy simulation (DES) and the acoustic pressure in the far-field is computed through the use of a Ffowcs Williams and Hawkings integral. Several surfaces of integration are used, both solid and permeable. The inlet design is based on an experimental inlet developed by the National Advisory Committee for Aeronautics (NACA). The flow is solved first through steady-state RANS simulation, then time-dependent DES is run from the converged results. The results from both RANS simulations and DES show good agreement with experimental data from NACA, both in terms of integral quantities and surface pressure coefficients. Pressure fluctuations are observed on both sides of the lip of the inlet, and are greater at low velocity ratios, with the velocity ratio defined as the ratio between the flow velocity at the duct entrance and in the free stream. A transition is observed between a quasi-laminar flow at a velocity ratio of 0.8 and a turbulent flow at velocity ratios of 0.6 and 0.4. This turbulent behavior at low velocity ratios is associated with much higher acoustic levels in the far-field. At low velocity ratios, the acoustic spectra in the far-field exhibit a broadband character with maximum levels distributed around a characteristic frequency given by the ratio between the flow velocity at the duct entrance and the duct entrance depth. At high velocity ratios, the spectra show tonal characteristics with peaks at around 90 percent of this characteristic frequency and at the corresponding harmonics. A comparison between the spectra from solid and permeable surfaces reveals that volume sound sources are negligible at this low Mach number. A visualization of the integrands of the Ffowcs Williams and Hawkings integral shows that sound sources are located on both sides of the lip of the inlet, at the position of impact of the vortices, and along the vortex wakes. Some observations regarding the use of solid and permeable surfaces of integration are made.

Monte Carlo simulations of the relative biological effectiveness for DNA double strand breaks from 300 MeV u−1 carbon-ion beams

Monte Carlo simulations are used to calculate the relative biological effectiveness (RBE) of 300 MeV u−1 carbon-ion beams at different depths in a cylindrical water phantom of 10 cm radius and 30 cm long. RBE values for the induction of DNA double strand breaks (DSB), a biological endpoint closely related to cell inactivation, are estimated for monoenergetic and energy-modulated carbon ion beams. Individual contributions to the RBE from primary ions and secondary nuclear fragments are simulated separately. These simulations are based on a multi-scale modelling approach by first applying the FLUKA (version 2011.2.17) transport code to estimate the absorbed doses and fluence energy spectra, then using the MCDS (version 3.10A) damage code for DSB yields. The approach is efficient since it separates the non-stochastic dosimetry problem from the stochastic DNA damage problem. The MCDS code predicts the major trends of the DSB yields from detailed track structure simulations. It is found that, as depth is increasing, RBE values increase slowly from the entrance depth to the plateau region and change substantially in the Bragg peak region. RBE values reach their maxima at the distal edge of the Bragg peak. Beyond this edge, contributions to RBE are entirely from nuclear fragments. Maximum RBE values at the distal edges of the Bragg peak and the spread-out Bragg peak are, respectively, 3.0 and 2.8. The present approach has the flexibility to weight RBE contributions from different DSB classes, i.e. DSB0, DSB+ and DSB++.

The features of ac magnetic susceptibility in thin superconducting films with a high critical current

The features of ac magnetic susceptibility appearing in thin superconducting films with a high critical current were investigated for the first time. These features were found in some films of YBa2Cu3O7–δ in magnetic-field and temperature dependencies of the ac susceptibility in the form of Z-like step for the real component, χm′(H) or χm′(T), and V-like dip for the imaginary component, χm″(H) or χm″(T), where the index m indicates measurements at a maximum of the polar diagram χ′′(χ′) (“maximum of losses”). Out of the maximum of losses the effect is also observed and its value depends on the depth of entrance and exit of vortices. It is suggested that the effect is caused by dependencies of the critical current and flux creep on a magnetic field. The magnetic susceptibility for a thin disk was calculated approximately using modified Clem-Sanchez formulas, in which a dependence of the critical current density on the applied field, jc(H), was introduced. The calculations based on the real dependence jc(H) in the films studied and with a simplest account for the flux creep allowed to obtain the dependencies χm′(H) and χm″(H), qualitatively similar to experimental, including the Z- and V-features at a large critical current. It is shown that for these samples the Clem-Sanchez relations between the critical current density, on the one hand, and components of the ac magnetic susceptibility and also the amplitude of the ac field at the maximum of losses, on the other hand, are violated.

Use of one-dimensional modelling in estuary management: entrance depth –– model calibration

The Wairoa River, a barrier enclosed estuary situated in Hawke’s Bay, New Zealand was modelled using a one-dimensional hydrodynamic model. Water level data obtained during a flood and a bathymetric survey were available but the entrance cross-section had not been surveyed. This paper describes the calibration of the model to jointly optimise the selection of the Manning coefficient and the depth of the estuary entrance.

Monte Carlo simulation of single-plane magnetically focused narrow proton beams

We present Monte Carlo simulations of magnetically focused proton beams shaped by a single quadrapole magnet. Such beams are narrowly focused in one longitudinal plane but fan out in the perpendicular plane producing elongated elliptical beam spots (a ‘screwdriver’ shape). The focused beams were compared to passively collimated beams (the current standard of delivery for small radiosurgery beams). Beam energies considered were relevant to functional radiosurgery and standard radiosurgery clinical applications. Three monoenergetic beams (100, 125, and 150 MeV) and a modulated beam were simulated. Monoenergetic magnetically focused beams demonstrated 28 to 32% lower entrance doses, 31 to 47% larger central peak to entrance depth dose ratios, 26 to 35% smaller integral dose, 25 to 32% smaller estimated therapeutic ratios, 19 to 37% smaller penumbra volumes, and 38 to 65% smaller vertical profile lateral penumbras at Bragg depth, compared to the collimated beams. Focused modulated beams showed 31% larger central peak to entrance dose ratio, and 62 to 65% smaller vertical lateral penumbras over the plateau of the spread out Bragg peak. These advantages can be attributed to the directional acceleration of protons in the transverse plane due to the magnetic field. Such beams can be produced using commercially available assemblies of permanent rare earth magnets that do not require electric power or cryrogenic cooling. Our simulations suggest that these magnets can be inexpensively incorporated into the beam line to deliver reduced dose to normal tissue, and enhanced dose to elongated elliptical targets with major and minor axes on the order of a few centimeters and millimeters, respectively. Such beams may find application in novel proton functional and standard radiosurgery treatments in and around critical structures.

Integrating a MRI scanner with a 6 MV radiotherapy accelerator: impact of the surface orientation on the entrance and exit dose due to the transverse magnetic field

At the UMC Utrecht, in collaboration with Elekta and Philips Research Hamburg, we are developing a radiotherapy accelerator with integrated MRI functionality. The radiation dose will be delivered in the presence of a lateral 1.5 T field. Although the photon beam is not affected by the magnetic field, the actual dose deposition is done by a cascade of secondary electrons and these electrons are affected by the Lorentz force. The magnetic field causes a reduced build-up distance: because the trajectory of the electrons between collisions is curved, the entrance depth in tissue decreases. Also, at tissue–air interfaces an increased dose occurs due to the so-called electron return effect (ERE): electrons leaving tissue will describe a circular path in air and re-enter the tissue yielding a local dose increase. In this paper the impact of a 1.5 T magnetic field on both the build-up distance and the dose increase due to the ERE will be investigated as a function of the angle between the surface and the incident beam. Monte Carlo simulations demonstrate that in the presence of a 1.5 T magnetic field, the surface dose, the build-up distance and the exit dose depend more heavily on the surface orientation than in the case without magnetic field. This is caused by the asymmetrical pointspread kernel in the presence of 1.5 T and the directional behaviour of the re-entering electrons. Simulations on geometrical phantoms show that ERE dose increase at air cavities can be avoided using opposing beams, also when the air–tissue boundary is not perpendicular to the beam. For the more general case in patient anatomies, more problems may arise. Future work will address the possibilities and limitations of opposing beams in combination with IMRT in a magnetic field.

Electrochemical and corrosion protection properties of ion implanted thin films

Ion implantation offers the possibility to alloy the surface-near region of metals with noble metals which increase the corrosion resistance of the system. Due to the limited entrance depth of ions into solids, the modified zone is generally very thin. The observable effects are therefore usually not long-lasting because the resistant alloy is consumed too fast. However, for special corrosion conditions a long-term protection may be obtained. Tantalum suffers from hydrogen embrittlement when it corrodes in hot concentrated mineral acids, and titanium and stainless steel from active corrosion with high dissolution rates in activating mineral acids. Electrochemical and immersion tests show that implantation of electrocatalytically active noble metals such as platinum and palladium may lead to an effective protection over a longer duration of time. For comparison, results on uniform corrosion of iron in slightly acidic media are also discussed.

EXPERIENCE WITH SELF-DREDGING HARBOUR ENTRANCES

About 7 years ago, the Department of Public Works of Canada requested the assistance of the National Research Council to devise a means of reducing sediment deposition in the entrance to a small harbour at Dmgwall, Nova Scotia. Siltation of this harbour entrance, which opens to the Atlantic, was so severe that on occasions it was completely blocked by sand at low tides. The desired objective was to devise a layout of structures which would maintain an entrance depth of 12 feet at low tide. Model studies were carried out and a breakwater configuration was evolved which appeared to have some "selfdredging" characteristics. The recommended structures were built in 1962 and to date have been successful in maintaining minimum depths of 5 feet at low tide which is adequate for the fishing fleet using the harbour. While falling somewhat short of the original objective this performance has been very satisfactory when compared with the conditions which existed before construction. Similar installations have since been built at two other locations in Nova Scotia Which are on the Gulf of St. Lawrence. Indications so far are that similarly satisfactory results have been obtained. This paper describes the installations, makes some tentative suggestions concerning the mechanisms involved m their operation and provides data on their performance.