Narrow Bridge Research Articles

A Study of the Drainage Capacity, Flood Risks and Mitigation Measures for Selected Areas in Guyana’s Coastal and Riverine Regions: Williamsburg- Hampshire, Kilcoy-Chesney and Mabaruma-Kumaka-Barabina

This research investigates the drainage challenges and flood risks in three areas of Guyana: Williamsburg-Hampshire, Kilcoy-Chesney, and Mabaruma-Kumaka-Barabina. These drainage areas are characterised by low-lying terrain, proximity to waterways, and inadequate drainage infrastructure. The study identifies how these factors lead to frequent and sometimes costly flooding, especially during periods of peak rainfall and high tides that prevent the opening of drainage sluices. Using rainfall and runoff data, with the analysis of drainage coefficients and discharge capacities, the study examines the existing drainage systems in these regions. It highlights the inefficiencies of undersized drainage structures, inadequate maintenance, and the growing pressure from urbanisation, which has led to the expansion of impervious surfaces, thus increasing runoff. In the case of Mabaruma-Kumaka-Barabina, under- maintained sluices, narrow bridge culverts, and low earthen dams exacerbate the area’s flood vulnerabilities. To address these issues, the study recommends several key interventions. These include upgrading drainage infrastructure by widening internal drains, replacing narrow culverts, installing additional sluices, and using modern technologies like automated pumps and self-actuated sluices. The construction of higher, vegetated embankments and raising the earthen river dams are also recommended to prevent erosion and overtopping during high tides. Monitoring water levels and rainfall data regularly is proposed to inform drainage maintenance and flood prevention efforts. The findings underscore the need for public-private partnerships to maintain drainage systems while engaging the community in flood risk mitigation. By implementing these recommendations, these regions can better manage water flow, reduce the impact of flooding, and improve the quality of life for residents, particularly as climate change continues to pose greater challenges for water management in Guyana.

Utilizing data-driven algorithms for blind modal parameter identification of structures from output-only video measurements

In structural dynamics and vibration analysis, modal identification plays a pivotal role in understanding and characterizing the dynamic behavior of complex systems. Traditional modal analysis techniques heavily rely on accurate sensor placement and knowledge of the excitation forces, which may not always be feasible or practical in real-world scenarios. Recently, non-contact video-based modal analysis methods for structures with arbitrary complexity using computer vision techniques have gained much importance. But these methods need to know ahead of time where the structure's natural frequency ranges are, and they use steerable pyramids, which are complicated multi-scale image decomposition filters. To address these issues, a blind modal identification technique is suggested to extract the modal parameters (modal frequency and mode shapes) from the recorded structural vibration video signal. The proposed algorithm for unsupervised machine learning is the Non-Negative Matrix Factorization (NNMF) method, which is combined with the Generalized Complexity Pursuit (GCP) method for blind source separation. The NNMF algorithm is directly applied to the raw pixel-time series made from the video data to get the temporal components, which are then separated using GCP to find the individual modal frequencies and mode shapes. The above algorithm is first validated on a numerical model and then implemented on laboratory scale models (cantilever, single-degree, and multi-degree frame models). Finally, the proposed methodology is implemented on real-world recorded structural vibration videos to determine its noise sensitivity, such as the Tacoma Narrows bridge and the London Millennium footbridge. The modal parameters extracted are compared with those from the available literature for validation. The estimation errors obtained from all the validations are well below 1%, which makes the technique quite suitable and reliable for structural vibration monitoring by identifying and reproducing complex vibration modes.

The collapse of the Tacoma Narrows bridge-- Why?

In 1940, a new bridge over the Tacoma Narrows south of Seattle went into violent oscillation for over an hour and then collapsed, with the loss of one dog's life. The bridge satisfied all of the engineering standards but the first windy day doomed it. What happened? A variety of explanations have been advanced, but the cause turned out to be quite simple, though unexpected. (It was not resonance.) There are many similarities between it and the fundamental playing behaviour of wind instruments, a positive feedback mechanism coupling the bridge to the wind. (It was not resonance.) In 2006, Daniel Green and I, using a finite element program of G. Morgenthal, showed what triggered this positive feedback mechanism in the case of the bridge, and this talk will discuss the features of our explanation

Automata-based Software Engineering for Control System Design and Verification

The automata composition is defined as the basic language construct of automata programming. Incorporating automata composition into an arbitrary programming language allows the development of automata programs in that language. Methods for specification and verification of reactive systems are defined in detail. All kinds of correctness formulas for a reactive system with respect to its specification are defined. In addition, correctness formulas for verification using the full invariant of the reactive system are developed. The Event-B manual begins with a brilliant illustration of the basic Event-B methods using the example of a car traffic control problem on a narrow bridge. However, the latter refinement in this illustration generates a complex cumbersome program. A simpler and shorter solution to this problem was presented in our work [7] using automata programming approach. Our solution was not easy because 4 non-trivial bugs were found by verification in Event-B. This paper describes our third attempt to construct a short simple automata program to solve this problem. Verification of the automata program in Event-B and Why3 systems was carried out. No errors were found. For verification, a reactive system model is built on Why3, which is simpler and more universal than the why3-do model.

C4 (Clinical Case) Vascular Ehlers-Danlos Syndrome in the Paediatric Population: A Case Report of an Internal Bleed Caused by Ruptured Pseudoaneurysm

Abstract Introduction/Background Ehlers-Danols syndrome (EDS) is a connective tissue disease characterized by joint hypermobility, skin hyperextensibility and tissue fragility. EDS has six types. Type IV EDS: vascular EDS (vEDS), is rare but also the most malignant. Case Description We report a 15-year-old boy with a previous history of spontaneous colon perforation and two left shoulder dislocations. He presented with sudden onset abdominal pain, vomiting, dizziness, and lethargy with a Glasgow coma scale of 13. His abdomen was soft but mildly tender. He had a capillary refill of 3 seconds with cold extremities, was found to be in a hypotensive shock state requiring resuscitation with fluids and inotropes, as well as intubation and mechanical ventilation. His hemoglobin dropped by 30 g/L in 6 hours. Therefore, an abdominal ultrasound was done, revealing an intrabdominal hematoma. CT scan of the abdomen confirmed a ruptured fusiform pseudoaneurysm of the accessory left hepatic artery. This was successfully managed by coil embolization, see F1 and F2, below. Genetic workup was positive for the pathogenic COL3A1 gene that presents phenotypically as Ehlers-Danlos syndrome, particularly type IV. Discussion COL3A1 encodes pro-alpha1 chains of type III collagen. Inheritance is autosomal-dominant. It can present as a de novo variant with a negative family history, as was the situation for our patient. Estimated affected people with de novo variant vEDS is 33%-50%. Clinical diagnosis of vEDS involves one major and several minor criteria (2017). Major criteria include arterial aneurysms, dissection, or rupture; intestinal rupture; uterine rupture during pregnancy; family history of vEDS. Minor criteria include easy bruising; thin skin and visible veins; facial characteristics including prominent eyes, narrow nasal bridge, thin lips; club foot, congenital hip dislocation; inguinal hernia and pneumothorax. Our patient had two elements from the major criteria: arterial pseudoaneurysm and intestinal rupture. Conclusion vEDS has high morbidity and mortality due to the risk of spontaneous internal organ/vessel injury. This can be mitigated by increased awareness of systemic manifestations of vEDS and a high index of suspicion by both primary care and emergency physicians. Once diagnosed, surveillance is crucial, including regular blood pressure monitoring, frequent non-invasive imaging to identify emerging vascular lesions, and pregnancy counselling for potential uterine rupture and avoiding trauma, collision sports, and lifting heavy items.

Precursor of disintegration of Greenland's largest floating ice tongue

Abstract. The largest floating tongue of Greenland’s ice sheet, Nioghalvfjerdsbræ, has been relatively stable with respect to areal retreat until 2022. Draining more than 6 % of the ice sheet, a disintegration of Nioghalvfjerdsbræ's floating tongue and subsequent acceleration due to loss in buttressing are likely to lead to sea level rise. Therefore, the stability of the floating tongue is a focus of this study. We employed a suite of observational methods to detect recent changes at the calving front. We found that the calving style has changed since 2016 at the southern part of the eastern calving front, from tongue-type calving to a crack evolution initiated at frontal ice rises reaching 5–7 km and progressing further upstream compared to 2010. The calving front area is further weakened by an area upstream of the main calving front that consists of open water and an ice mélange that has substantially expanded, leading to the formation of a narrow ice bridge. These geometric and mechanical changes may be a precursor of instability of the floating tongue. We complement our study by numerical ice flow simulations to estimate the impact of future ice-front retreat and complete ice shelf disintegration on the discharge of grounded ice. These idealized scenarios reveal that a loss of the south-eastern area of the ice shelf would lead to a 0.2 % increase in ice discharge at the grounding line, while a sudden collapse of the frontal area (46 % of the floating tongue area) will enhance the ice discharge by 5.1 % due to loss in buttressing. Eventually, a full collapse of the floating tongue increases the grounding line flux by 166 %.

Theoretical and numerical decay results of a viscoelastic suspension bridge with variable exponents nonlinearity

AbstractStrong vibrations can cause considerable damage to structures and break materials apart. The main reason for the Tacoma Narrows Bridge collapse was the sudden transition from longitudinal to torsional oscillations caused by a resonance phenomenon. There exists evidence that several other bridges collapsed for the same reason. To overcome unwanted vibrations and prevent structures from resonating during earthquakes and winds, features and modifications such as dampers are used to stabilize these bridges. In this work, we study a nonlinear viscoelastic plate equation with variable exponents, which models the deformation of a suspension bridge. First, we establish explicit and general decay results of the system depending on the decay rate of the relaxation function and the nature of the variable‐exponents nonlinearity. Then, we perform several numerical tests to illustrate our theoretical decay results. Our results extend and generalize many earlier works in the literature.

Validation of Synthetic Design Hydrographs through 2D hydrodynamic modelling

The procedure for the determination of Synthetic Design Hydrographs (SDHs), proposed in previous works, is validated by comparing the peak discharges obtained by routing a long series of historical floods and the synthetic floods at different stations along a complex river system.At this aim, the 60 km long terminal stretch of the Dora Baltea river (Northern Italy) has been modelled according to fully 2D high resolution hydrodynamic approach. The fluvial branch is of considerable complexity due to a strong contraction induced by the presence of a narrow Roman bridge, which, during the most important flood events, causes the reactivation of a paleochannel and the flooding of a part of the city of Ivrea. The hydraulic model has been calibrated on the basis of the main historical floods. Then, all the historical floods over a period of more than 80 years (1939–2020) and the SDHs derived by the same series have been routed. Historical and synthetic peak discharges at two downstream stations have been then compared in probability plots. The results show that the peak discharge distributions derived by routing the historical floods and the SDHs compare well. This suggests that SDHs construction procedure is reliable and has statistical significance.

Large wood debris that clogged bridges followed by a sudden release. The 2019 flash flood in Catalonia.

Study regionFrancolí River (Catalonia, Iberian Peninsula). Study focusThe aim is the reconstruction of the October 2019 flash flood, that was documented through extensive field work: rainfall (300 mm in just a few hours), flood marks, times of flood passage and witnesses' snapshots and reports, channel changes, log drift (20,000 trees) and woody debris at bridges, as well as large damage and six fatalities. The methods are: hydrological model built for the rainfall-runoff in the basin and the flood routing in the river, use of hydraulic principles such as flow at waterfalls, flow against obstacles (trees), etc. and finally 1D/2D free surface numerical models. New hydrological insightsThe uppermost 100 km2 produced discharges of 700 m3/s (up to 50 m3/s/km2, locally). Three bridges failed, but their cascading failure (when one failure triggers the next one downstream) was not proved. The main channel widened more than 10 times, dragging away soil and vegetation like a bulldozer. The resulting large wood debris that clogged two bridges worsened the inundation. An anomalous flow downstream, probably a surge of around 1090 m3/s, due to the failure of a woody jam at a narrow bridge, took two lives. Water Authority is now warning flood planners that vegetated, torrential basins may cause catastrophic floods in the valley towns, if their narrow bridges are sensitive to woody debris.

Wreathed in Worry, Pining for Protection: Latino Forestry Workers and Historical Traumas in Maine

Most of the workers in the van were sleeping because of the early morning hour, but Edilberto Morales-Luis was feeling nervous. Their driver—who was trying to cover the three-hour commute to the forest quickly to compensate for lost time due to rain—was barreling down a dirt road amid gusty winds. “Why don't you drive a little bit slower?” Morales-Luis called out, only to have a co-worker tease him for being afraid. It was September 12, 2002, and the crew of fourteen Guatemalan and Honduran H-2 visa guest workers had been hired to thin trees and clear brush for six months in Aroostook County, a remote part of northern Maine bordering Canada. They were working for Evergreen Forestry Services, an Idaho-based reforestation company subcontracting for the Maine-based Seven Islands Land Company.1 As the driver, Juan Turcios-Matamoros, transferred from the dirt road onto Johns Bridge, a narrow 260-foot wooden bridge with no guardrail perched over the Allagash Wilderness Waterway, the right side of the van missed the bridge planks and caught on an outer row of steel bolts. The tires started shredding. Startled, several passengers implored him to slow down; they were less than five miles from their destination. Instead of braking, Turcios-Matamoros maintained his speed and tried to steer the right wheels back onto the planks but overcorrected. The van took a sickening skid before flipping over and plunging off the bridge into the whirling water beneath. Shocked but aware he needed to act quickly, Morales-Luis swam to the back of the van, kicked out the rear window, and pushed his way out. “I fought to get [the rest of] them out of there. But I couldn't,” he later said. The van filled rapidly with water, and the fourteen other men—who included his own uncle—sank to the river bottom. Edilberto swam to shore to get help, but the accident had happened so far from any trafficked roadway that he had to wait half an hour to flag down a passing vehicle. It then took almost four hours for rescue crews to arrive. The state police and national guard deployed helicopters and floatplanes, and rescuers were able to eventually heave the van—which still held the bodies—out of the water and onto a large flatbed truck. Juan Perez-Febles, an employee of the Maine Department of Labor's Migrant and Immigrant Services Division, joined a caravan of vehicles that escorted the truck to the Maine Medical Examiner's Office. There, he saw the victims' bodies jumbled together with saws, blades, gasoline cans, and lunch pails. “The tangled mess of flesh, vomit coming out of their mouths…. You could see the panic in their faces,” he said. Perez-Febles stayed at the office to interpret for the lone and stressed survivor, Morales-Luis, who identified his co-workers and reconstructed the accident for officials and the media.2

High-resolution Radio Study of the Dragonfly Pulsar Wind Nebula Powered by PSR J2021+3651

The Dragonfly Nebula (G75.2+0.1) powered by the young pulsar J2021+3651 is a rare pulsar wind nebula (PWN) that shows double tori and polar jets enclosed by a bow-shock structure in X-rays. We present new radio observations of this source taken with the Very Large Array at 6 GHz. The radio PWN has an overall size about two times as large as the X-ray counterpart, consisting of a bright main-body region in the southwest, a narrow and fainter bridge region in the northeast, and a dark gap in between. The nebula shows a radio spectrum much softer than that of a typical PWN. This could be resulting from compression by the ram pressure as the system travels mildly supersonically in the interstellar medium. Our polarization maps reveal a highly ordered and complex B-field structure. This can be explained by a toroidal field distorted by the pulsar motion.

Liquid EBG-Backed Stretchable Slot Antenna for Human Body

For the first time, liquid metal is incorporated with an elastomer platform for designing an electromagnetic bandgap (EBG)-backed wearable antenna that can be placed on human body. Here, the liquid metal (EGaIn) is injected into a soft and stretchable Ecoflex 0030 substrate for making a fluidic slot antenna and a liquid EBG (LEBG) structure. The LEBG is then placed at the back of the slot antenna for mitigating the effects of human body and improving the antenna performance. It has an antenna gain of 5.80 dBi in the boresight and a low specific absorption rate (SAR for 1 g U.S. standard) of 1.25 W/kg. Since liquid metal is highly dense, the ground plane of the LEBG is separated into six segments, which are connected through narrow bridges. Due to the use of such design, the wobbly effect of the dense liquid metal can be reduced significantly. The measured impedance bandwidth (3.23–3.59 GHz) of the proposed antenna is very stable and not affected much by its own structural deformation on human body. Since the elastomer platform is waterproof, it makes the antenna characteristics very stable in humid environment, which is a very desirable feature for wearable antennas.

Physical Models: Their Historical and Current Use in Civil and Building Engineering Design ed. by Bill Addis (review).

Reviewed by: Physical Models: Their Historical and Current Use in Civil and Building Engineering Design ed. by Bill Addis David F. Channell (bio) Physical Models: Their Historical and Current Use in Civil and Building Engineering Design Edited by Bill Addis. Berlin: Wilhelm Ernst & Sohn, 2021. Pp. 1113. Readers of Technology and Culture will find a great deal of useful information in this edited collection but may also find some frustrations. The focus of the book is the somewhat neglected subject of the role of physical models in the history of design from ancient times to the present. The editor argues that physical models provide a way for designers to convey ideas to those who build engineering artifacts and to provide a way to test that the designed artifact will function as intended. As such, physical models represent a crucial "third strand" along with theory and practice in the development of engineering science. Nearly half of the book deals with physical models that were developed from ancient times through the 1930s. The book has a very large number of photographs, drawings, charts, graphs, and other illustrations that allow the reader to more fully understand how the models function and their role in engineering design. The book is well organized, first focusing on historical time periods and then on specific design projects such as Filippo Brunelleschi's design of the dome of Florence Cathedral, Leonhard Euler's model for a bridge in St. Petersburg, the models used in the Conway and Britannia tubular bridges in Great Britain, and the use of models in the design of the Boulder Dam. With only a few exceptions, the contributors to the volume are trained in engineering or architecture. The editor has a Ph.D. in the history and philosophy of engineering along with a background in the aerospace industry. A small number of contributors have some training in the history of architecture, but aside from the editor only one or two contributors have backgrounds in the history of technology. Because of this, much of the literature on the history of technology that involves modeling and structures, such as works by Edwin Layton, Terry Reynolds, Walter Vincenti, David Billington, and Eda Kranakis, among others, are not cited in the volume. Not surprisingly, given the backgrounds of the contributors, the volume follows a very internalist approach to the history of physical models. With the exception of some discussion of testing laboratories, there is almost no engagement with the idea of contextual history. There is little discussion of how physical models have been shaped by society and culture and how society and culture have been shaped by the use of different types of physical models. While the idea of physical models as a "third strand" in shaping engineering science is mentioned in the preface, there is no continuing or broad analysis of how the development of physical models have interacted with theory of practice to contribute to the development of engineering science. [End Page 1250] While the volume covers a tremendous amount of material, there are some surprising topics that are not covered. For example, the chapter on the development of arch construction during the ancient period makes almost no reference to the Roman use of the arch and subsequently the dome. The chapter on wind tunnels tends to focus on testing buildings and bridges and therefore neglects any discussion of the Wright brothers' use of wind tunnel testing. Many major bridge projects, such as the Conway and Britannia bridges and the Tacoma Narrows Bridge, are covered, but there is no discussion of the Brooklyn Bridge. But if a reader wants to gain an almost encyclopedic knowledge of the technical details of almost any type of physical modeling, this book would be a very useful resource. David F. Channell David F. Channell received his Ph.D. in the history of science and technology from Case Western Reserve University and is currently professor of history/history of ideas at the University of Texas at Dallas. His newest book is George Wilson's Vision of Early Victorian Science and Technology (Routledge, 2022). Citation: Channell, David F. "Review of Physical Models: Their Historical and Current Use in Civil and Building Engineering...

Vertical and torsional vibrations before the collapse of the Tacoma Narrows Bridge in 1940

We perform a three-dimensional direct numerical simulation of flow over the Tacoma Narrows Bridge to understand the vertical and torsional vibrations that occurred before its collapse in 1940. Real-scale structural parameters of the bridge are used for the simulation. The Reynolds number based on the free-stream velocity and height of the deck fence is lower ( ${Re}=10\ 000$ ) than the actual one on the day of its collapse ( ${Re}=3.06 \times 10^{6}$ ), but the magnitude of a fluid property is modified to provide the real-scale aerodynamic force and moment on the deck. The vertical and torsional vibrations are simulated through two-way coupling of the fluid flow and structural motion. The vertical vibration occurs from the frequency lock-in with the vortex shedding, and its wavelength and frequency agree well with the recorded data in 1940. After saturation of the vertical vibration, a torsional vibration resulting from the aeroelastic fluttering grows exponentially in time, with its wavelength and frequency in excellent agreement with the recorded data of the incident. The critical flutter wind speed for the growth of torsional vibration is obtained as $3.56 < U_c / (f_{nat} B) \le 4$ , where $U_{c}$ is the critical flutter wind speed, $f_{nat}$ is the natural frequency of the torsional vibration and $B$ is the deck width. Finally, apart from the actual vibration process in 1940, we perform more numerical simulations to investigate the roles of the free-stream velocity and vertical vibration in the growth of the torsional vibration.

An anillin-CIN85-SEPT9 complex promotes intercellular bridge maturation required for successful cytokinesis.

Cleavage of one cell into two is the most dramatic event in the life of a cell. Plasma membrane fission occurs within a narrow intercellular bridge (ICB) between the daughter cells, but the mechanisms underlying ICB formation and maturation are poorly understood. Here we identify CIN85 as an ICB assembly factor and demonstrate its requirement for robust and timely cytokinesis. CIN85 interacts directly with the N-terminal region of anillin and SEPT9 and thereby facilitates SEPT9-containing filament localization to the plasma membrane of the ICB. In contrast, the C-terminal pleckstrin homology (PH) domain of anillin binds to septin units lacking SEPT9 but enriched in SEPT11. Anillin's interactions with distinct septin units are required to promote ICB elongation and maturation that, we propose, generate the physical space into which the abscission machinery is recruited to drive the final membrane scission event releasing two independent daughter cells.

Dynamical Anyon Generation in Kitaev Honeycomb Non-Abelian Spin Liquids.

Relativistic Mott insulators known as "Kitaev materials" potentially realize spin liquids hosting non-Abelian anyons. Motivated by fault-tolerant quantum-computing applications in this setting, we introduce a dynamical anyon-generation protocol that exploits universal edge physics. The setup features holes in the spin liquid, which define energetically cheap locations for non-Abelian anyons, connected by a narrow bridge that can be tuned between spin liquid and topologically trivial phases. We show that modulating the bridge from trivial to spin liquid over intermediate time scales-quantified by analytics and extensive simulations-deposits non-Abelian anyons into the holes with O(1) probability. The required bridge manipulations can be implemented by integrating the Kitaev material into magnetic tunnel junction arrays that engender locally tunable exchange fields. Combined with existing readout strategies, our protocol reveals a path to topological qubit experiments in Kitaev materials at zero applied magnetic field.

Monitoring the Condition of Narrow Bridges Using Data from Rotation-Based and Strain-Based Bridge Weigh-in-Motion Systems

Monitoring the Condition of Narrow Bridges Using Data from Rotation-Based and Strain-Based Bridge Weigh-in-Motion Systems

An Irish Dante, Part I: Possible Precursors to the Commedia

An Irish Dante, Part I: Possible Precursors to the Commedia Daragh O’Connell (bio) 2021 marked the septicentennial celebrations of Dante’s death in Ravenna. Despite the restrictions brought about by the global pandemic, scholars and creative practitioners around the world ensured that the anniversary did not pass unnoticed, with online and in-person conferences, seminars, readings, performances, adaptations, translations and dialogues taking place on a daily basis. In Ireland too Dante’s anniversary was marked by a series of initiatives both scholarly and creative: the establishment at University College Cork of the Centre for Dante Studies in Ireland foregrounded a series of activities and research initiatives, including the Dante Dialogue Series of 2021;1 the Irish artist Liam Ó Broin exhibited his Dante-inspired 100 lithographs, Dante’s Divine Comedy, at Dublin Castle; and the musician and composer Elliot Murphy premiered his Dante’s Inferno on 30 September 2021.2 Though the Florentine poet never once mentions Ireland in his masterpiece, which he called simply the Commedia (the ‘Divine’ appellation is a much later addition), there is a curious sense in which Ireland played a not-insignificant role in both the poem’s rich imaginary landscape and in its afterlife in the creative sphere, providing an Irish Dante via Yeats, Joyce, Beckett and Heaney that ‘achieves things that are beyond the grasp of the English or Americans’.3 Why Dante and Ireland? What links Dante to this island specifically? Let me state from the outset that Ireland’s relationship with Dante is uniquely special; our experiencing of Dante is one that is protean, indeed vital to the creative energies of our best artists, mostly the literary ones. In Part II of this essay, I will trace the presence of Dante in Irish literature of the twentieth century and after. First, however, in Part I, I must turn to the rich Irish medieval tradition of vision literature, which in some cases predates Dante by several centuries, to see possible direct and indirect influences emerge. In some cases these texts stand as eloquent precursors to Dante’s poem. Since our very earliest literature in Ireland, the afterlife – its representations and configurations (Navigatio Sancti Brendani; Visio 125 Tnugdali) – [End Page 125] has exerted an enduring hold on the Irish imagination and indeed influenced European cultural expression in the Middle Ages. But let’s start in purgatory – St Patrick’s, that is. Umbiferi prefazi (Paradiso, XXX, 78) – Shadowy prefaces Legend states that while St Patrick was on Station Island he had a vision of the afterlife in a cave on the island. Station Island is an island in Lough Derg, in County Donegal. Legend attributes the colour of the lake (‘Red Lake’ in Irish) to the blood of a monster-serpent killed by St Patrick. Station Island has long been a place of Catholic pilgrimage. In 1184 a monk, who signed himself ‘H’ at the monastery of Saltrey near Cambridge, wrote about the experiences of the Irish knight Owein during his visit to Lough Derg: the Tractatus de Purgatorio Sancti Patricii.4 Some forty years before H penned his story, Owein was allowed to enter the cave on the island and soon found himself surrounded by demons and cast into the fire. He was delivered by calling on the name of Christ. After multiple periods of torture, the knight finally made his way across a narrow bridge over hell and entered an earthly paradise, where souls await their entry into heaven. Owein returned to the world to tell others of his ordeal. Various versions and translations of the story became widely read across Europe. No one knows the source of Owein’s visions. One possibility is that medicinal (‘purgative’) herbs were burned in the cave. Some of these could have led to hallucinations. Ireland has evidence of ancient ‘sweathouses’ that were likely used in this way. The idea of St Patrick’s purgatory became famous, and Lough Derg soon became a popular place of pilgrimage. The Tractatus became arguably the most popular vision of purgatory in the Middle Ages and was quickly disseminated across Europe through vernacular translations. There is clear evidence in Italy of this identification of St Patrick with purgatory. One of...

Wind-Induced Instability Mechanism of Old Tacoma Narrows Bridge from Aerodynamic Work Perspective

Postflutter limit cycle oscillations (LCOs) are typical nonlinear aeroelastic phenomena for bridge girders. An H-shaped section with a roughly 5:1 aspect ratio, treated as a simplified section of the Old Tacoma Narrows Bridge, was chosen for wind-induced instability re-evaluation, considering its vibration amplitude-dependent aerodynamics characteristics and nonlinear structural damping effects from the energy perspective of aerodynamic work. Forced vibrations at large torsional amplitudes in a wind tunnel were realized with the help of an improved forced motion apparatus (FMA), and synchronous measurements of forces and displacements on the FMA were achieved. Self-excited forces (SEFs) were extracted, and an energy map showing quantitative relationships between vibration amplitude, reduced velocity, and aerodynamic work acting on the section were established. Furthermore, the postflutter LCOs phenomena originating from the energy balance between nonlinear aerodynamic work input and energy consumption by structural damping effects were reillustrated, and nonlinear structural damping effects of prototype bridges are therefore discussed. Moreover, the instability paths of the bridge were investigated by the energy map, considering its vibration amplitude-dependent aerodynamics and structural damping effects from an aerodynamic work perspective. The results show that LCO velocity basically increases with vibration amplitude at different structural damping ratios in torsional degree of freedom, characterizing postflutter LCOs phenomena. The structural damping ratio at the bridge’s collapse is also re-estimated as about 0.0115 with better coincidence of on-the-spot observation and theoretical analysis. In addition, both the aerodynamic damping ratio considering nonlinear characteristics of the SEFs and the structural damping ratio basically increasing with vibration amplitude contribute to postflutter LCOs phenomena of the Tacoma Bridge. The instability paths of the bridge essentially rely on the competitive relationships between structural damping ratios, structural stiffness degeneration, and oncoming wind velocities in the process of collapse.

Beach Area Development Strategy as the Prime Tourism Area in Indonesia

This research aims to study and analyze the appropriate strategies carried out and developed by stakeholders to build and develop the coastal area of Cemara Sheet as a mainstay tourist area in West Lombok. The development of the coastal regions is significant to create community welfare and educate it to take responsibility and maintain the preservation of the marine environment and the natural surroundings. The research approach used is a qualitative descriptive approach based on field observations supported by secondary data. The collected data is then analyzed using a SWOT analysis by systematically identifying various internal and external factors to formulate the desired development strategy. The logic that is built is how to maximize strengths (Strengths) and opportunities (Opportunities) but simultaneously minimize weaknesses (Weaknesses) and threats (Threats). The results showed that the tourism object of Cemara beach is very potential to be developed because of the natural support of the beach and sea and the surrounding hills. It has a clean and beautiful beach, the mangrove forest, which is still beautiful. In the background, it has an attractive green spread of Sekotong hills, a strategic position as the entrance to Lombok from the sea route, and its safe and comfortable environment. But on the other hand, several things need improvements, such as structuring the housing environment for residents, handling waste, and compliance with tourist facilities such as trash cans, ATMs, toilets, mini markets, prayer rooms, and others. Facilities and infrastructure and supporting infrastructure need attention to be better organized, such as the construction of water games, outbound, and viewing posts. Damaged and narrow road and bridge infrastructure, street and beach lighting are also necessary fixed. If all of these things can be handled properly, then the Cemara beach tourism object will charm and become a mainstay tourist destination that can compete with other tourist objects.