Search Results (71)

This study proposes a balanced truck dispatching strategy for inter-terminal transportation (ITT) in large ports, incorporating proactive demand outsourcing to address stochastic and imbalanced ITT demand. A portion of ITT tasks are intentionally outsourced to third-party public trucks at a higher cost, so that self-owned trucks can be reserved for more critical tasks. The ITT system is modeled as a closed Jackson network, in which self-owned trucks circulate among terminals and routes. An optimization model is developed to determine the optimal proactive outsourcing ratios for origin–destination terminal pairs and the appropriate fleet size of self-owned trucks, aiming to minimize total transportation costs. Reactive outsourcing is also included to handle occasional truck shortages. A mean value analysis method is used to evaluate system performance with given decisions, and a differential evolution algorithm is employed for optimization. The case study of Shanghai Yangshan Port demonstrates that the proposed strategy reduces total system cost by 9.8% compared to reactive outsourcing. The results also highlight the importance of jointly optimizing outsourcing decisions and fleet size. This study provides theoretical insights and practical guidance for ITT system management under demand uncertainty. Full article

A grid-connected converter is the interface between renewable energy power generation systems, such as solar power generation, wind power, hydropower, etc., and the power grid, responsible for the stable and efficient transmission of electric energy generated by renewable energy power generation systems to the grid. In order to realize local access for distributed photovoltaic power generation devices and energy storage devices, a composite three-port converter has the advantages of small size, low cost and high power density compared with a combined three-port converter. In view of the current problems of the existing compound three-port (AC/DC/DC) converters, such as DC and AC circulating current in current composite three-port converters and the harmonic control problem, the proposed compound three-port topology consists of a full-bridge inverter with six switching tubes, a zigzag transformer, two sets of filter inductors and two filter capacitors. Among them, the power frequency transformer adopts the zigzag connection method, which can effectively restrain the AC circulation and eliminate the DC magnetic flux of the iron core while introducing the third port. Firstly, the principle of AC/DC and DC/DC power conversion in the composite three-port topology is analyzed, which has higher efficiency than other topologies. Secondly, the topology control strategy is analyzed, and a two-loop hybrid current control method with improved current loop is proposed. When the DC-side voltage fluctuates, the DC offset of the battery can effectively improve the stability of the network side. Through the MATLAB/Simulink simulation experiment platform, the high efficiency of energy conversion and stable grid-connected operation characteristics are verified. Finally, the experiment of integrating into the power grid was carried out. Experiments were used to verify the effectiveness and feasibility of the proposed topology and strategy. The experimental results show that Total Harmonic Distortion (THD) can be controlled below 3%. Full article

A series (n = 22) of glasses from the site Kapucinski vrt (garden of the Capuchin monastery, 5th–17th c. CE) in Koper (Capodistria), a port town in the northern Adriatic, was measured using a combined PIXE and PIGE method. Koper has been continuously populated since the late Roman period, with a rich medieval history, thus offering an opportunity to study Early Medieval glass. Stemmed goblet fragments, in the original publication dated between the 6th–9th centuries CE, and several other vessel types (beakers and flasks or bottles and lamps) were selected for analysis. The measurements were expected to show the trends in glass production and consumption from Late Antiquity until the Middle Ages, notably the transition between natron to plant ash glass and the supply of fresh glass. Among the set of 22 glass vessel fragments, both natron and plant ash glass were identified. For finer classification, we relied on a newly developed method of Euclidean distances with respect to major concentrations. Natron glass of the types Foy 2.1 (9 examples), Magby (2 examples), and Levantine I (Apollonia; 2 examples) was found. Two glasses remain undetermined but testify to an Egyptian origin. Most natron glasses show signs of recycling. Among the three unrecycled glasses (about 20% of the whole set), there are two examples of Levantine glass and a Magby glass lamp; this may indicate a modest supply of fresh glass during the period. Plant ash glass may be attributed to the Early or High Middle Ages, exploiting the purified alkalis of the Levantine coasts (known as alume catino in later Venetian glassmaking), and the admixture of impurities in the siliceous sands suggests the circulation and consumption of glass that was produced and traded in the eastern Mediterranean since the 10th century CE. Full article

Circulating cell-free DNA (cfDNA) has emerged as a compelling candidate of liquid biopsy markers for the diagnosis and prognosis of several cancers. We systematically reviewed data on the role of cfDNA markers in the diagnosis, prognosis and treatment of hepatocellular carcinoma (HCC). Early studies suggested that levels of circulating cfDNA, mitochondrial DNA and cfDNA integrity are higher in patients with HCC than chronic liver diseases. In subsequent studies, methylation changes in circulating tumor DNA (ctDNA) as well as cfDNA fragmentation patterns and circulating nucleosomes were found to offer high sensitivity (>60%) and excellent specificity (>90%) for HCC diagnosis. The predictive role of cfDNA markers and ctDNA has been assessed in a few studies including untreated patients with HCC providing promising results for prediction of survival. However, port-hepatectomy detection of cfDNA/ctDNA markers or copy number variation indicators of cfDNA seem to reflect minimum residual disease and thus a high risk for HCC recurrence. The same markers can be useful for prediction after transarterial chemoembolization, radiofrequency ablation, radiotherapy and even systemic therapies. In conclusion, cfDNA markers can be useful in HCC surveillance, improving early diagnosis rates, as well as for monitoring treatment effectiveness and minimal residual disease post-treatment. Full article

The Talbot effect concerns the periodic self-imaging along an optical axis of a free-space optical field that is periodic in an initial transverse plane. It may be modeled by a shift-invariant linear system, fully characterized by the convolution of its impulse response. Self-imaging at integer and fractional Talbot distances of point sources on a regular grid in free space may then be represented by a transmission matrix that is circulant, symmetric, and persymmetric. The free-space Talbot effect may be mapped to the Talbot effect in a multimode waveguide by imposing the anti-symmetry of the mirror-like sidewalls created by the tight confinement of light within a high-index contrast multimode waveguide. The position of the anti-symmetry axis controls the distribution of discrete lattice points in a unit cell. For different distributions, interesting features such as conditional flexibility in the placement of access ports without altering amplitude and phase relationships, omitting ports without power penalty, closed form uneven splitting ratios, and offset access ports can be derived from the MMI coupler. As a specific example, a simple $2\times 2$ MMI coupler is shown to provide a power-splitting ratio related to the golden ratio $\phi$. The structure is amenable to planar photonic integration on any high-index contrast platform. The predictions of the theory are confirmed by simulation and verified by experimental measurements on a golden ratio MMI coupler fabricated using an SOI process. Full article

The coastal regions of major bay areas—including San Francisco, Tokyo, New York, Guangdong–Hong Kong–Macao, and Hangzhou—are important centers of economic and social growth due to their strategic location, resources, and dynamic economies. However, the significant development disparities between the central cities and surrounding areas, as well as the challenges of climate change, highlight the need for a comprehensive assessment of their development potential. The aim of this study is to find out which cities have the strongest development potential and what the main factors influencing the results are. To address this research question, we use a combination of the Analytic Hierarchy Process (AHP) and the Entropy Weight Method (EWM) to systematically assess the development potential of 63 cities in five bay area regions and explore the mechanisms that influence it. The principal component analysis (PCA) also examines the global networking and sustainability mechanisms. The results show that Shenzhen and Shanghai lead in development potential due to strong institutional frameworks and global connectivity, but significant imbalances remain in the bay areas. Key contributors to sustainability and connectivity include air passenger traffic, public libraries, and port handling, while traditional economic metrics such as GDP growth show limited impact. These findings underscore the importance of prioritizing urban livability, resource circulation, and infrastructure over traditional economic indicators for sustainability and provide actionable insights for policy makers to promote balanced and sustainable development in bay area cities. Full article

The water quality in port domains is highly dependent on the capacity for renewal and mixing with external water. This study uses Lagrangian modelling to investigate renewal time in Barcelona, Tarragona, and Gijón harbours (Spain), which represent semi-enclosed micro-tidal and meso-tidal environments. For this purpose, different particle-tracking simulations have been carried out in each of the ports to study the trends of circulation and water renewal trends both on the surface layer and at the bottom. The results indicate that in microtidal Mediterranean ports, the renewal time is longer at the bottom (32 days in Barcelona and 61 days in Tarragona). Conversely, in the mesotidal port of Gijón, located on the Cantabrian coast, the opposite pattern is observed, with higher renewal times at the surface (14 days). While the results from Lagrangian modelling exhibit magnitudes comparable to in situ measurements from previous studies, it remains essential to evaluate the specific characteristics of each method and compare these findings with other similar works. Full article

Sulfur dioxide (SO₂) can be of natural and anthropogenic origin and is one of the sulfur compounds present in the atmosphere. Among natural sources, volcanoes contribute with relevant annual outputs, and major eruptions lead to spikes in these outputs. In the case of anthropogenic pollution, SO₂ emissions are mostly correlated with the sulfur content of fuels, which has been the focus of specific emission mitigation policies for decades. Following other examples of cyclic and multi-year evaluations, an analysis of SO₂ at the Lamezia Terme (code: LMT) WMO/GAW (World Meteorological Organization—Global Atmosphere Watch) station in Calabria, Southern Italy, was performed. The coastal site is characterized by wind circulation patterns that result in the detection of air masses with low or enhanced anthropic influences. The presence of the Aeolian Arc of active, quiescent, and extinct volcanoes, as well as Mount Etna in Sicily, may influence LMT observations with diffused SO₂ emissions. For the first time in the history of the LMT, a multi-year analysis of a parameter has been integrated with TROPOMI data gathered by Sentinel-5P and used to test total tropospheric column densities at the LMT itself and select coordinates in the Tyrrhenian and Ionian seas. Surface and satellite data indicate that SO₂ peaks at the LMT are generally linked to winds from the western–seaside wind corridor, a pattern that is compatible with active volcanism in the Tyrrhenian Sea and maritime shipping to and from the Gioia Tauro port located in the same region. The findings of this research provide the basis for enhanced source apportionment, which could further differentiate anthropogenic sources in the area from natural outputs. Full article

Ports are the main arteries of global trade, handling goods circulation and serving as hubs for information, capital, and technology. Integrating digital technology has become the key for green port development to achieve resource efficiency and ecological balance. The current literature overlooks how digital technology can facilitate greener port operations. This study integrates sustainable supply chain management and system dynamics theories based on an in-depth analysis of existing research results and expert interviews. The analysis focuses on three key dimensions: integrating digital technologies with infrastructure, optimizing digital management and operations, and improving environmental and safety management in a digitally driven setting. Using the fuzzy Decision Making Trial and Evaluation Laboratory (Fuzzy Dematel) methodology, we collaborated with domain experts in port logistics to identify and confirm 12 pivotal factors that support the green digital transformation of ports. The research shows that the most critical success factors for using digital technology to drive ports’ green transformation are green supply chain information platforms, intelligent vessel scheduling, traffic optimization, and digital carbon emission monitoring. This study significantly contributes to the literature on green port transformation, offering indispensable practical insights for port operators, government entities, and shipping firms in identifying and deploying these key success factors. The findings will help maritime supply chain stakeholders develop actionable digital strategies, improving port efficiency and ecological resilience. Full article

Using industry standard TSMC 90 nm CMOS technology, a broadband and high-isolation active quasi-circulator MMIC was fabricated to meet the needs of future communication system integration. An active balun and phase inverter stage made of a common-source (CS) field-effect transistor (FET) comprised the quasi-circulator that was suggested. A cascade CS stage was used to produce the active balun, which increased the isolation of |S12| and |S23| through the unilateral characteristic of the FET and allowed for transmission of |S21| and |S32|. Further, a CS FET connected in parallel to ports 1 and 3 for phase cancellation can effectively increase the quasi-circulator’s isolation |S31|. Theoretical analysis for the detailed circuit was shown in the main paper. The results show that all isolations are better than 20 dB over 5–33 GHz, and the measured findings reveal that the suggested quasi-circulator has an insertion loss of less than 10 dB. It is possible to reach an isolation level of 55 dB between ports 1 and 3, which is greater than present research. Full article

In recent years, the Port of Topolobampo, Sinaloa, Mexico, has experienced unusual free sea surface elevations, particularly during the months of November and December, affecting the shipyard areas, service docks, and berthing locations. This study focuses on analyzing the oscillatory behavior of free surface elevations in shipyard regions. A hydrodynamic model was employed to simulate the circulation and sea surface agitation, aiming to quantify the elevation magnitudes based on oceanographic and meteorological data from November of the preceding year. A 30-day numerical simulation was conducted, revealing the velocity fields associated with coastal currents and tides during November, as well as the interaction between incident waves and wave transformations due to protective structures. The results demonstrated accurate behavior in 95% of the simulation period, while anomalous elevations exceeding those specified in the design and operational guidelines of the Port of Topolobampo were observed during the final five days of the simulation. An ANOVA test was performed between the surface elevation and vertically integrated velocity to assess whether the deviations in the last five days were statistically significant compared to the rest of the simulation period. With a P-value of less than 0.05, the null hypothesis of no difference was rejected, confirming a significant variation. These findings suggest that the extreme values recorded should be considered for the potential redesign of shipyard infrastructure. Full article

The meteorology of cutoff lows over South Africa is characterized by statistical analysis of daily field data in the period 1970–2023. An index is formulated by subtracting 500 hPa geopotential height in the mid-latitudes from the subtropics. Cutoff lows (COL) are identified by positive values, mostly in autumn and spring. Statistics indicate that climate forcing is seasonal: La Nina/El Nino favors COL in March–May/September–November. Hemispheric regressions reveal anomalous highs across the southern mid-latitudes when COL are frequent over South Africa. A 14-case composite was formed from the most intense daily COL events in autumn and spring. The composite shows a NW- tilted Rossby wave and jet stream loop around the COL. Maritime easterlies induce a warm east—cool west SST pattern, but composite moist inflows are shallow, so stormy weather hugs the coastal plains. Overturning circulations meet in an upper-level “saddle” over South Africa. 500 hPa sinking motions to the Southwest are of similar strength to rising motions to the Northeast. A COL case study exhibited hourly rain rates >10 mm at Port Alfred 18–20 October 2012 fed by tropical inflow. New insights emerged from this study via composite height sections over South Africa. Full article

This paper presents a design of a X-band circulator–isolator for handling high-peak-power applications. The device consists of two cascade-connected ferrite circulators, with one dedicated to transmission and the other to small-signal reception coupled with high-power signal isolation. To improve the power capacity, a layer of poly-tetra fluoroethylene (PTFE) film is placed above and below the circulator’s and the isolator’s center conductors. Measurement results show that the device is capable of withstanding a peak power of 7000 W, with an insertion loss of <0.3 dB at the transmitting port. Similarly, it sustains a peak power of 6000 W with an insertion loss of <0.5 dB at the reception port. Moreover, the proposed design achieved isolation between the transmitting and receiving ends of >20 dB with a VSWR < 1.2 at each port. Thermal analysis shows that the maximum relative ambient temperature rise is 15.11 ${ }^{\circ }$C. These findings show that the proposed device achieves low-loss transmission of high-peak-power signals in the transmit channel and reverse isolation of high-peak-power signals in the receive channel. Full article

Modular multilevel converters with non-sinusoidal ac voltage output can reduce cost and volume in medium-voltage-connected electric vehicle battery charging applications. The use of full-bridge submodules in such converters enables single-stage ac/ac voltage conversion, allowing a medium-voltage grid to be directly connected to a medium-frequency isolation transformer. The application of a square wave voltage at the medium-frequency transformer’s single-phase port enhances the converter’s efficiency and power density in comparison to a sinusoidal voltage. This paper presents the analysis and modelling of a modular multilevel converter, comparing its operation with sinusoidal and square wave output voltages. A single control scheme for both output voltage waveforms is proposed for the three-phase and single-phase ac currents, circulating currents, and the energy stored in the submodule capacitors. The control strategy of the three-phase and single-phase port currents is verified through simulation and experiments using a scaled-down prototype, thereby validating its suitability for high-power bidirectional battery chargers. Full article

The research work explores the impact of temperature on Silicon photovoltaic (PV) panels, considering Nigeria as a case study. It is found that high solar radiation in Nigeria increases the surface temperature of PV panels above 25 °C of the optimal operating temperature. The redundant energy gain from solar irradiance creates heat at the rear of solar panels and reduces their efficiency. Cooling mechanisms are therefore needed to increase efficiency. In this study, we demonstrated a unique hybrid system design employing a heat exchanger at the back of the panel, with water circulated through the back of the PV panel to cool the system. The system was simulated using TRNSYS at three locations in Nigeria—Maiduguri, Makurdi, and Port Harcourt. The results of the peak annual electrical power output in Maiduguri give a power yield of 1907 kWh/kWp, which is the highest, due to a high solar radiation average of 727 W/m² across the year. For Makurdi, the peak annual electrical power output is 1542 kWh/kWp, while for Port Harcourt the peak power output is 1355 kWh/kWp. It was observed that the surface temperature of Polycrystalline Si-PV was decreased from 49.25 °C to 38.38 °C. The electrical power was increased from 1526.83 W to 1566.82 W in a day, and efficiency increased from 13.99% to 15.01%. Full article