Wave Hydrodynamics across Steep Platform Reefs: A Laboratory Study

This paper presents a laboratory study on wave transmission across steep platform reefs, aiming at furthering knowledge of wave hydrodynamics and establishing empirical formulations of spectral wave parameters across the reef flat. The ultimate aim of this study is to determine the design wave load to design fixed offshore structures on coral reefs flat. The process of wave transmission across the underground coral strip with a large front slope has been studied on a physical model in the wave trough with nearly 300 experimental cases combined from 05 underground band models and many random wave scenarios and scenarios at different submerged depths. Experimental results show that the abrupt transition in depth from deep water ahead to relatively shallow water in the reef is responsible for the difference in the wave at the top of the strip compared to the wave on the normal beach, especially regarding the statistical distribution of the wave height. Breaking waves at the abrupt transition have deviated the wave height distribution curve from the deep-water (Rayleigh) theoretical distributions and even the existing shallow-water distributions, including the effect of breaking waves. Two sets of empirical formulations of the spectral wave parameters (Hm0 and Tm-1, 0) are eventually derived for the surf zone and the region behind the surf zone, respectively. These local wave parameters can be used as inputs to a wave height distribution model for determining other design characteristic wave heights on steep platform reefs. Doi: 10.28991/CEJ-2022-08-08-015 Full Text: PD

The initial study of EBNA-2 polymorphisms in nasopharyngeal carcinoma in Vietnam

Epstein-Barr virus (EBV) infection is the main cause of Nasopharyngeal Carcinoma (NPC). EBNA-2, one of the most important genes participating in the formation of NPC, also helps EBV evade an attack on the immune system. EBNA-2 has 4 variants including E2-A, E2-B, E2-C and E-2D, of which E2-A and E2-C are the characterized variants for NPC. This study aimed to evaluate the variations of EBNA-2 in NPC biopsy samples of Vietnamese patients. This initial study used 10 biopsy samples, which were positively confirmed to NPC, collected from Cho Ray Hospital. Nested PCR – nucleotide sequencing was applied to analyze the variants of EBNA-2. The results showed that 8 out of 10 samples, accounting for 80%, were positive to EBNA-2. Additionally, only two variants, E-2A and E-2C were detected in our study, in which, E2-A subtype was identified as the predominant subtype. These findings would provide initial data about potential contribution of EBNA-2 polymorphisms to etiology of NPC in Vietnamese population

Radio Detection of the Sun

The radio emission of the Sun has been measured using a radio interferometer including two Yagi antennas operated at 610 MHz. We report the observation of interferences and comment on the results

Reduction in Plasmodium falciparum Pfk13 and pfg377 allele diversity through time in southern Vietnam

Background: Plasmodium falciparum has acquired resistance to artemisinin in Southeast Asia, with mutations in the P. falciparum Kelch-13 (Pfk13) gene associated with the resistance phenotype. The widespread use of Artemisinin-based combination therapy (ACT)s in Southeast Asia has led to the selection and spread of parasites carrying mutations in Pfk13. We characterised the allele diversity of Pfk13 and pfg377, an artemisinin-resistance neutral polymorphic gene, in parasite DNA extracted human blood from in southern Vietnam in 2003, 2012, 2015 and 2018.Method: This study was conducted in Bu Gia Map commune, Binh Phuoc province, Vietnam, from May 2018 to January 2019. Twenty-four samples from 2018 to 2019, 30 from 2003, 24 from 2012 and 32 from 2015 were analysed. Malaria-infected human blood was collected by finger-prick and used for molecular analysis. A nested-PCR targeting the small subunit ribosomal RNA gene was used for Plasmodium species identification, followed by amplification and nucleotide sequencing of Pfk13 and region 3 of pfg377. Archived blood samples collected in the same region in 2012 and 2015 were also analysed as above for comparison.Results: The genetic diversity of Pfk13 and pfg377 was lower in 2018–2019 compared to 2012 and 2015. The number of distinct Pfk13 mutants decreased from three in 2012 and 2015, P553L, V568G and C580Y, to one, C580Y in 2018–2019. In 2018–2019, the frequency of C580Y mutant strains was 71% (17/24 isolates). All samples were wild type in 2003. In 2012 and 2015, there were single-strain infections as well as co-infections with two mutant strains or with mutant and wild strains, whereas there were no co-infections in 2018. pfg377 allele diversity decreased from five alleles in 2012 to two alleles in 2018–2019.Conclusion: The genetic diversity of P. falciparum was reduced at the two genetic loci surveyed in this study, Pfk13 and pfg377. In the case of the former gene, we observed an increase in the prevalence of parasites carrying the C580Y gene, known to confer reduced susceptibility to ACTs. The reduction in the diversity of pfg377 may be linked to the clonal expansion of parasite strains carrying the C580Y mutation, leading to an overall reduction in parasite genetic diversity across the population

Seasonal breaching of coastal barriers

Natural or unintended breaching can be catastrophic, causing loss of human lives and damage to infrastructures, buildings and natural habitats. Quantitative understand-ing of coastal barrier breaching is therefore of great importance to vulnerability as-sessment of protection works as well as to spatial planning against flooding hazards. The main objective of the present research is to develop a reliable process-based nu-merical model of coastal barrier breaching, which is capable of simulating both the breach initiation during storm surges and the barrier breaching due to overflow. The model is limited to homogeneous coastal sand barriers or similar types only, such as sand-dikes and sand dunes. The newly-developed model is referred to as a site model, i.e. the simulation domain is restricted to a representative cross-section of a barrier and the question where in plan a breach will occur is not answered by the model.Civil Engineering and Geoscience

Cooperation between Networked Multiple Robots for Exploration

In multiple mobile robot system, cooperation among robots usually executes through communication. With the advance in technology nowadays, each robot can be equipped with off-the-shelf wireless device following the standard IEEE 802.11. However, due to the limitation of transmission range as well as the complexity of environment and signal transmission, maintaining connection between a pair of robots while they are executing their tasks becomes difficult. We construct a wireless ad hoc network multi mobile robots system with consideration of continuous connection between two robots, the Leader and any Follower. Also, our algorithm can be applied to a group of mobile robots when we utilize the wireless environment to establish continuous sharing of information among the robots. In order to enhance the system’s performance, we build a communication framework using the multicast technique. By using this framework, one robot can easily exchange its data with others when coordination is needed. Furthermore, when keeping the connection between two robots, we enhanced the teaming stability of the whole system. Finally, with our framework we create a flexible mobile robot system in which every robot can minimize the energy in communication with the rest of team. The overall performance is validated in the simulation system and experiment.Table of Contents Acknowledgments I Abstract III Table of Contents V List of Figures VII Chapter 1 Introduction 1 1.1. Motivation 1 1.2. Brief Literature Review 3 1.3. Contribution 5 1.4. Thesis Organization 6 Chapter 2 Preliminaries 9 2.1. Wireless Network 9 2.1.1. Wireless Local Area Network (Wireless LAN) 9 2.1.2. Wireless IEEE 802.11 Architecture and Protocols 12 2.1.3. Properties of Wireless Transmissions 14 2.2. Ad-hoc Network for Mobile Robots 16 2.2.1. Need for Ad hoc Robotic Network 17 2.2.2. Characteristic Features of Wireless Ad hoc Robot Network 18 2.2.3. Ad hoc Routing Protocol 19 2.2.4. Ad hoc Robotic Network Architecture 22 2.3. Transmission Protocols 24 2.3.1. The TCP Connection 24 2.3.2. Connectionless Transport UDP 25 Chapter 3 Communication in multiple mobile robots 27 3.1. Problems in Communication between Robots 27 3.2. Methods in Maintaining/recovering Communication 29 3.2.1. Rally Point 30 3.2.2. Communication Recovery Behaviors 32 3.2.3. Value-based Communication Preservation (VBCP) 33 3.2.4. Perceived Signal Strength based Method 35 3.3. Mobility Models and the Impact on Connection Stability 37 3.3.1. Mobility Patterns 37 3.3.2. Entity Mobility Models 41 3.3.3. Group Mobility Models 45 3.3.4. Influence of Mobility 48 Chapter 4 Cooperation between Networked Multi-robot System 53 4.1. Coordination for Exploration 53 4.1.1 Frontier Cell and Occupancy Grid Map 54 4.1.2 Cost of Reaching a Target Location 56 4.2 Algorithm to Maintain Communication between Networked Mobile Robot 57 4.2.1 Mobility Prediction 57 4.2.2 Controllable Parameters 59 4.2.3 Threshold Values 60 4.2.4 Strategy for Robot’s Behavior 61 4.2.5 Controller Design 63 Chapter 5 Experiment and Simulations Results 71 5.1 Winsock API and Programming Model 71 5.1.1 Winsock API 71 5.1.2 Winsock Programming Model 73 5.2 Communication Framework built on UDP and Multicast 74 5.2.1 Purpose of Building a Communication Framework 74 5.2.2 Implementation of Building a Communication Framework 75 5.3 Results with the Group of 2 robots 78 5.4 Results with the Group of 3 robots 82 Chapter 6 Conclusion and Future Work 85 6.1 Conclusion 85 6.2 Future Work 86 References 8

Proces-based modeling of the overflow induced growth of erosional channels

A new process-based approach is introduced for a more efficient computation of the overflow-induced growth of an erosional channel in a noncohesive homogeneous narrow landmass such as the breach growth in a sand-dike. The approach is easy to incorporate in a 1D/2DV morphodynamic model to compute the channel growth both vertically and laterally. The flow modeling is based on the shallow water equations. For modeling the channel growth, a set of closed equations describing the channel growth in both vertical and lateral direction has been derived in connection with several new morphologic parameters such as the representative channel width and the channel cross-sectional growth index. The approach has been applied to simulate the breach growth in sand-dikes and the morphological development of wave overwash across sand barriers. The computational results bear fairly good resemblance with existing experimental data.Hydraulic EngineeringCivil Engineering and Geoscience