•We describe a new mathematical formulation for the unidirectional QCSP with stability constraints (QCSPVS) based on trim stability.•We propose an efficient logic-based Benders approach to optimally ...solve the QCSPVS.•We present extensive computational experiments on benchmark instances aimed at validate the effectiveness of the proposed model and solution approach.
This paper addresses the quay crane scheduling problem (QCSP) with vessel stability constraints. Vessel stability is essential to improve quay crane operations in container terminals, but it significantly complicates the basic QCSP and the corresponding solutions methods. We describe a novel mathematical formulation for the unidirectional QCSP with vessel stability, and we propose an exact algorithm based on logic-based Benders decomposition to solve the problem efficiently. The problem is decomposed into two subproblems, e.g., a task-assignment master problem without vessel stability constraints, and a time-allocation problem, aimed at determining the operation time of each task under the premise of the vessel stability requirements. The proposed algorithm is tested on benchmark instances derived from the literature, and the effectiveness of the proposed model and solution approach is demonstrated.
Purpose
Bridging stent stability is crucial for efficacy and safety of branched aortic endovascular repair (bEVAR) of thoracoabdominal aortic aneurysms (TAAAs). In this study, we assess the ...performance of the new Viabahn Balloon-Expandable endoprosthesis (VBX) in bEVAR. Based on our learning curve we give recommendations for a safe and effective use of the device.
Materials and Methods
We prospectively collected the data of patients with TAAAs undergoing bEVAR between December 2017 and December 2019. All patients with implantation of at least 1 VBX stent-graft as bridging stent were included in our single-center analysis. Demographic, comorbidity, and computed tomography angiography (CTA) data of 112 patients were retrospectively evaluated. Primary endpoint was a composite of branch-related technical success and freedom from target vessel instability. Secondary endpoints were clinical and ongoing clinical success.
Results
Primary endpoint: technical success was achieved in all patients (100%) with a freedom from target vessel instability of 96.3% after a median follow-up of 18 months. Overall mortality was 13.4% (n=15) and 13 patients underwent secondary interventions, 12 of them are still alive and 1 suffered from aneurysm sac expansion, consequently an ongoing clinical success of 75.9% was reached. After modification of the implantation technique during the course of the study by selecting longer stent lengths after accurate estimation of vessel curvature and expected adaptation of the flexible endoskeleton to the specific anatomical conditions, no type Ic endoleaks were observed in the last 70 cases.
Conclusions
The VBX stent-graft can be safely used as bridging stent for branched thoracoabdominal repair. However, learning curve should be considered to avoid type Ic endoleak and edge stenosis. Based on this experience longer landing zones and 2-step deployment of VBX are useful for successful bridging also of challenging target vessels.
Maintaining the stability and maturation of blood vessels is of paramount importance for the vessels to carry out their physiological function. Smooth muscle cells (SMCs), pericytes, and mesenchymal ...stem cells (MSCs) are involved in the maturation process of the newly formed vessels. The aim of this study was to investigate whether transforming growth factor beta 1 (TGF-β1) treatment could enhance pericyte-like properties of dental pulp stem cells (DPSCs) and how TGF-β1-treated DPSCs for 7 days (T-DPSCs) stabilize the newly formed blood vessels.
We utilized TGF-β1 to treat DPSCs for 1, 3, 5, and 7 days. Western blotting and immunofluorescence were used to analyze the expression of SMC markers. Functional contraction assay was conducted to assess the contractility of T-DPSCs. The effects of T-DPSC-conditioned media (T-DPSC-CM) on human umbilical vein endothelial cell (HUVEC) proliferation and migration were examined by MTT, wound healing, and trans-well migration assay. Most importantly, in vitro 3D co-culture spheroidal sprouting assay was used to investigate the regulating role of vascular endothelial growth factor (VEGF)-angiopoietin (Ang)-Tie2 signaling on angiogenic sprouting in 3D co-cultured spheroids of HUVECs and T-DPSCs. Angiopoietin 2 (Ang2) and VEGF were used to treat the co-cultured spheroids to explore their roles in angiogenic sprouting. Inhibitors for Tie2 and VEGFR2 were used to block Ang1/Tie2 and VFGF/VEGFR2 signaling.
Western blotting and immunofluorescence showed that the expression of SMC-specific markers (α-SMA and SM22α) were significantly increased after treatment with TGF-β1. Contractility of T-DPSCs was greater compared with that of DPSCs. T-DPSC-CM inhibited HUVEC migration. In vitro sprouting assay demonstrated that T-DPSCs enclosed HUVECs, resembling pericyte-like cells. Compared to co-culture with DPSCs, a smaller number of HUVEC sprouting was observed when co-cultured with T-DPSCs. VEGF and Ang2 co-stimulation significantly enhanced sprouting in HUVEC and T-DPSC co-culture spheroids, whereas VEGF or Ang2 alone exerted insignificant effects on HUVEC sprouting. Blocking Tie2 signaling reversed the sprouting inhibition by T-DPSCs, while blocking VEGF receptor (VEGFR) signaling boosted the sprouting inhibition by T-DPSCs.
This study revealed that TGF-β1 can induce DPSC differentiation into functional pericyte-like cells. T-DPSCs maintain vessel stability through Ang1/Tie2 and VEGF/VEGFR2 signaling.
•The primary cause of most incidents can be attributed to operators’ decisions that are detrimental to stability.•Near misses were used to supplement this data. Near misses, however, proved difficult ...to collect.•Discussions with operators highlighted the impact training has on an individual’s understanding of stability and the decisions they make while fishing.•Reduction in capsizing events in Canada may be attributed to training requirements become more strict.•Confident that improved training among operators will lead to a significant reduction in capsizing events in the future.
Commercial fishing is one of the most dangerous industries in the world. Although fishing vessel capsizes are rarely occurring events, they result in a disproportionally high fatality rate. In Canada, such fatalities are a significant problem. This study’s objectives are to determine the primary causes of fishing vessel capsizing and recommend measures to reduce the frequency of fishing vessel capsizes. A significant part of the data collection for the study is focused on the fishing industry in Newfoundland and Labrador, Canada, although the conclusions are more widely applicable. Through an analysis of national and international fishing vessel capsizing accident investigation reports, the study identifies the primary causes of capsizing events. In 57 of the 60 capsizes analyzed, operators’ actions played a significant role. Through interviews and discussions with fishing vessel operators, this data was supplemented and reinforced with a preliminary investigation of capsizing near-misses. The concept of near-miss reporting has been successfully used in other industries to identify hazards and improve safety culture. The study also focused on operator and crew understanding of vessel stability. This revealed a correlation between the amount of formal training an operator had received and their understanding of stability. Those who had received stability training were better equipped to avoid or manage potential capsizing events. Many fishing vessel capsize events were attributed to operator error and operators with no stability training are more likely to make poor decisions based on lack of knowledge or common misconceptions of vessel stability. A compulsory stability education course for the fishing industry is recommended along with a trial program of formalized near-miss reporting.
•A novel integrated vessel traffic and deballasting scheduling problem is studied.•Tidal fluctuation in the channel and vessel stability constraints are considered.•An integrated scheduling model to ...avoid loading interruption and reduce vessel delay.•Determine vessel sequences, lay-by berth allocation and deballasting plans simultaneously.•A total weighted delay reduction of 20.84% can be obtained compared to rule-based methods.
Most bulk carriers arrive at coal export terminals (CETs) under empty or lightly loaded conditions. Ballast water, which is onboarded to maintain vessel stability during a voyage, must be pumped out as the cargo is loaded. As modern CETs are rapidly developing, vessels’ deballasting capability is being updated too slowly and far behind the CET loading efficiency improvement. Therefore, an increasing number of vessels fail to finish deballasting in a timely manner, which results in frequent operational interruptions at the terminal. The high loading efficiency of modern CETs is discounted by a ship’s deballasting capability. Conventionally, many CETs have allowed vessels to deballast in advance at anchorages or lay-by berths to avoid delays at the loading berth and wasted resources. In this sense, in addition to making a complex traffic-scheduling plan for vessels entering and leaving terminals, port managers must make proper deballasting plans for vessels and avoid excessive deballasting problems. However, research on vessel scheduling considering deballasting is limited to date. To fill this gap, this paper proposes an integrated scheduling model (ISM) that manages the scheduling process of vessel traffic and deballasting operations. Special considerations of vessel stability under deballasting and tidal influence are introduced. As a result, with the goal of minimizing the total weighted delay, the model can simultaneously optimize the vessel sequence, lay-by berth allocation, and deballasting plan. A series of comprehensive experiments was conducted based on practical data collected from a major CET in China. The performance of the proposed ISM was tested through comparisons of scheduling under common rule-based scheduling methods with varying traffic density and terminal efficiency properties. The results show that the ISM can avoid untimely deballasting, shorten the vessel port stay time, and directly contribute to a total weighted delay reduction of 20.84%. Application of the ISM to address the conflict of unbalanced machinery upgrades between CETs and vessels at various stages is of great importance to guarantee improved port efficiency.
This study proposes a formulation to optimize operational efficiency of a dual-trolley quay crane and automatic guided vehicles (AGVs) to reduce energy consumption at an automated container terminal. ...A two-phase model is used to minimize energy consumption during loading and discharging operations, as well as maximize the utilization rate of the AGVs, with consideration of relevant constraints such as the capacity of buffers for the quay crane (QC) and yard, the stability of vessel, the maximum endurance of an AGV, and the available laytime for handling. We propose a constrained partial enumeration strategy to construct quay crane schedules and a genetic algorithm to solve the AGV scheduling problem. Finally, Yangshan Phase IV automated container terminal’s data is used to verify the validity and applicability of the proposed model. The results of the tests provide evidence that the proposed method can improve energy efficiency.
Angiogenesis is a deliberate sequence of events that starts with destabilization of an existing vascular bed, and ends when the newly generated vessels quiesce. During angiogenesis, endothelial cell ...growth, migration, and tube formation are regulated by pro- and anti-angiogenic factors, matrix-degrading proteases, and cell-extracellular matrix interactions. VEGF, arguably the best-studied angiomodulator, is highly regulated at the levels of synthesis, spatial distribution, receptor and co-receptor availability, and signaling downstream of the receptors. While many agents that contribute to angiogenesis have been identified and studied in depth, others, such as lysophosphatidic acid (LPA), are relatively unexplored.
This paper studies the Quay Crane Scheduling Problem (QCSP) that aims to find an optimized schedule for Quay Cranes (QCs) to load and unload containers onto and off of vessels. The resulting schedule ...has to satisfy certain technical requirements including crane safety margin and non-crossing constraint as well as vessel stability. We propose a two-stage solution method. In the first stage, we solve the problem without the vessel stability constraint using column generation method, and in the second stage, we adjust the obtained schedule when necessary, so that vessel stability is satisfied. A computational study demonstrates the effectiveness of the proposed method.
The location of a vessel's center of flotation during operation at sea plays an important role in the vessel's longitudinal stability. The ability to accurately estimate the location of the center of ...flotation improves safety monitoring as it indicates how changes in the distribution of weight affect the vessel. In this paper, we propose a novel method for estimating the longitudinal location of a vessel's center of flotation in waves using acceleration readings taken simultaneously at different locations along the length of the vessel. Specifically, we recorded accelerations of an autonomous surface vehicle (ASV) in a towing tank. The ASV was operated in head and following regular waves, which were kept at a constant wave height of 0.12 m while the wave frequency was increased from 0.5 to 0.8 Hz at increments of 0.1 Hz. The results show that multiple acceleration measurements can be used to correctly determine the center of flotation of a vessel in waves. In this experiment, the estimated location of the center of flotation varied as expected based on the longitudinal asymmetry of the ASV and the difference between head and following waves, demonstrating the effectiveness of the proposed method. In addition, the results were validated using the vessel's recorded pitch motion.
Vessel stability in polar low situations Orimolade, Adekunle Peter; Gudmestad, Ove Tobias; Wold, Lise Eide
Ships and offshore structures,
03/2017, Letnik:
12, Številka:
sup1
Journal Article
Recenzirano
An average of 12 polar lows develop yearly in the Norwegian and Barents Seas, when unstable air is accumulating over the ice-open water interphase. Polar lows are intense and rapid, accompanied by ...high wind speeds, large wave growth, and large snowfalls. There are uncertainties in polar low forecasts, and marine activities should not take place along the possible tracks of such events, even if the waves would be less than the extreme waves for the area. The metocean (meteorology and oceanography) conditions in polar lows suggest that a vessel at sea may experience severe sea spray icing. In this paper, we present vessel stability concerns, and the effect of snow and ice loads on stability, in polar low situations. Stability analysis results show that the additional snow and ice loads have more influence on smaller vessels' stability compared to larger vessels.
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