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Prediction of beach profile changes using spatiotemporal graph neural networks for beach morphological evolution modeling
No full textIn this study, a deep learning framework based on spatiotemporal graph neural networks (GNNs) is proposed to improve the prediction of beach morphological changes by effectively capturing nonlinear relationships and spatiotemporal dependencies among multiple input variables. The model is applied to the Wonpyeong (WP) region on the eastern coast of Korea, comprising four sandy beaches. It incorporates beach characteristics and oceanic forcing data collected through field surveys and ocean observations from 2010 and 2024, along with satellite optical imagery as supplemental remote sensing input. The WP region is subject to frequent anthropogenic interventions, such as submerged breakwater installation and beach nourishment, implemented to mitigate erosion resulting from coastal development. Accordingly, continuous monitoring and accurate morphological change prediction are critical for effective coastal management. An extensive set of ablation experiments was conducted to identify the optimal input variables, which include not only oceanic forcing factors, such as wave conditions and tidal levels, but also beach characteristics such as beach-face slope, median grain size, shoreline position, and cross-sectional profiles indicative of sediment transport and morphological change. To accommodate diverse temporal resolutions, variable-length data embeddings were developed for each input, along with a dedicated subnetwork for extracting shoreline features from satellite imagery. Despite abrupt anthropogenic alterations in beach morphology, the model exhibited robust predictive performance. Although it tended to underestimate bed level changes induced by artificial interventions, the predicted patterns of erosion, deposition, and shoreline movement aligned well with observed trends. Furthermore, the proposed model outperformed recently developed deep learning approaches in terms of prediction accuracy.11Nsciescopu
Acoustic characteristic analysis of small yellow croaker (Larimichthys polyactis) sounds
No full text해양 생물들은 의사소통, 먹이 탐색, 장애물 및 포식자 회피, 항해 등 여러 가지 목적을 위해 소리를 사용한다. 이러한 해양생물음은 개체군 평가, 행동 분석, 수중 은밀 통신 등 여러 연구 분야에 활용되고 있으며, 이를 위해서는 해양생물음의 음향학적 특성 분석이 선행되어야 한다. 본 연구에서는 소리를 발생시키는 어류 중 하나인 참조기(Larimichthys polyactis)가 내는 소리의 음향학적 특성을 분석하였다. 참조기 소리는 2024년 4월, 통영해상실증기지의 가두리 양식장에서 자동기록식 수중청음기를 활용하여 녹음되었다. 참조기 소리는 펄스 길이가 10 ms 이하의 펄스가 반복되는 형태를 보이고 파형이 매우 유사하게 나타났다. 이에 본 연구에서는 참조기 소리의 음향학적 특성으로, 하나의 신호 안에 존재하는 펄스 수, 펄스 간 간격, 펄스 간 간격의 변동성, 펄스 간 유사도를 분석하였으며, 신호별 대표펄스 길이, 반파장 개수, 음압 준위, 피크 주파수, 3 dB 대역폭을 분석하였다. 본 연구 내용은 향후 해양생물음 기반 응용연구에 기초 자료로 활용될 수 있다.33Nscopuskc
Load-resisting mechanisms and performance evaluation of heavy-duty block pavements: insights from laboratory and field tests
No full textThe increasing use of concrete block pavements in heavy-duty areas has led to the development of extended-dimension blocks for improved load resistance. However, construction standards and performance evaluations are limited. This study assessed port blocks with varying bedding thicknesses through laboratory and field tests. Repeated loading tests revealed that 80 mm bedding exhibited the highest relative deflection, indicating effective interlocking, whereas 50 and 110 mm beddings reduced interlocking, with 50 mm causing stress concentration and large deflections in unbound aggregate base (UAB). A test bed with 40 mm bedding was analysed, comparing UAB and cement-treated base (CTB) sections. Falling weight deflectometer tests and International Roughness Index indicated poor structural and functional performance of UAB, respectively, attributed to stress concentration at the base, as confirmed in laboratory tests. These findings highlight that port blocks require adjustments in bedding thickness according to base type to achieve effective interlocking.11Nsciescopu
Mechanical resistance of reinforced concrete beams strengthened by waste fishing net hybrid fiber-reinforced cementitious composites
No full textThis study experimentally investigates the flexural-shear performance of reinforced concrete (RC) beams strengthened with waste fishing net (W) hybrid fiber-reinforced cementitious composites (W-FRCCs), which has rarely been conducted in recent research and has not yet been addressed in existing standards and codes. Three-point bending tests are conducted on four series of RC beams strengthened and non-strengthened with W-FRCCs. Three types of strengthening layers are used to reinforce the RC beams, and five flexural parameters are evaluated. Although all RC beams failed under flexural-shear failure, using mortar with W textile (WT) and W short fiber (WF) is more effective in reinforcing conventional RC beams compared with using mortar and mortar with WT. The strengthening layers using mortar-reinforced WT and WF resulted in better performances compared with conventional RC beams. Additionally, the WT contributed significantly to load bearing from the initial stage up to a deflection of 4 mm, whereas the WF became effective beyond a 4-mm deflection due to the significantly higher stiffness and rigidity of the epoxy-treated WT compared to those of the WF. Moreover, using W-FRCCs in strengthening RC beams resulted in smaller crack widths compared with the case of non-strengthened RC beams because WF and WT delayed crack initiation and distributed stress more effectively. This strengthening method presents promising potential owing to the sustainable use of W, which can increase recycling rates and mitigate plastic pollution.11Nsciescopu
Four Marine Halacarids of Rhombognathus (Acari, Halacaridae) from Korea
No full textFour marine halacarid species belonging to genus Rhombognathus in the subfamily Rhombognathinae are newly reported from Korea: Rhombognathus arenarius Bartsch, 1992, R. ezoensis Abé, 1990, R. sinensis Bartsch, 1990, and R.
sinensoideus Bartsch, 1992. Specimens were collected from diverse habitats, including geniculate and non-geniculate red coralline algae from the East Sea, and brown algae, intertidal sandy sediments, and marine plastic debris from the coast of Jeju Island, Korea. These four Korean Rhombognathus species generally corresponded to their original descriptions, with some slight morphological differences observed in the number of male basilar perigenital setae and accessory processes on the lateral claws, the shape of the male posterior dorsal plate, and the distance between the anterior and posterior dorsal plates. This study provides supplementary descriptions, illustrations, and a key for four Rhombognathus species from Korea, as well as a comparative table of intraspecific variation among Korea specimens and those reported from their type localities and other regions. This study represents the first record of the genus Rhombognathus from Korea.22Ykc
CO2 Injection Well Cement Integrity Analysis for Geological CO2 Storage
No full text본 연구는 CO2 지중저장을 위한 심부 주입공에 사용되는 시멘트 안전성 분석을 위해 포틀랜드 시멘트와 G-Class 시멘트를 이용하여 역학적 및 수리적 물성을 측정하고 CO2 주입에 따른 시멘트 파쇄 양상과 주입성을 분석하였다. 해양 CO2 지중저장을 고려하여 바닷물을 사용하여 물/시멘트 중량비를 달리한 시멘 트에 기능성 첨가제를 첨가한 시멘트 시료를 제작하고 바닷물에 시멘트 시료를 양생하였다. 포틀랜드 시 멘트 및 G-Class 시멘트 모두 물/시멘트 중량비가 낮을수록 밀도가 높아 일축압축강도 및 영률 값이 높 아지는 경향을 보였다. 공극률의 경우 시멘트 종류에 상관없이 물/시멘트 중량비가 낮은 시료가 다소 높은 공극률 값을 보였으나 시멘트를 통한 누출 시 중요한 변수가 되는 투과도의 경우 중량비에 상관없이 G-Class 시멘트가 낮은 투과도 값을 보였다. 심부 저류층에 CO2 주입을 가정하여 주입 시 발생할 수 있는 주입공 주변 시멘트 파쇄 및 균열 발생 여부를 확인하기 위해 시멘트 CO2 파쇄 실험을 실시하였다. G-Class 시멘트가 포틀랜드 시멘트보다 높은 CO2 파쇄 압력을 보였다. 또한 CO2 주입공 주변부로의 누출 발생 여부를 확인하기 위해 CO2 주입공 케이싱 모사 시료와 저류층 모사 시료를 제작하여 CO2 주입 시 주입 압력 변화를 분석하였다. 이 연구 결과 G-Class 시멘트가 낮은 투과도, 높은 CO2 파쇄 압력, 주입압에 따른 안정적인 압력 변화 양상을 보여 CO2 지중저장을 위한 CO2 주입공 시멘트 안전성에 적합한 시멘트로 판단하였다.22Nkc
Temperature-Driven Intraspecific Diversity in Paralytic Shellfish Toxin Profiles of the Dinoflagellate Alexandrium pacificum and Intragenic Variation in the Saxitoxin Biosynthetic Gene, sxtA4
No full textAlexandrium pacificum, a globally distributed dinoflagellate, is well-known for causing harmful algal blooms and producing Paralytic Shellfish Toxins (PSTs), a threat to marine life and human health. The frequency and intensity of Alexandrium blooms have increased in recent decades, driven, in some cases, by increasing temperatures. Here, we investigated the temperature-dependent (15 °C, 20 °C, 25 °C, and 30 °C) growth rates and paralytic shellfish toxin profiles of eight A. pacificum strains while concurrently examining differences in sequences of the saxitoxin biosynthetic gene, sxtA4. While maximum cell densities were lowest at 30 °C, toxin production per cell was highest at higher temperatures that inhibited growth, with greater diversity of toxin analogs peaking at 30 °C, as confirmed by the higher Shannon’s diversity index obtained for the toxin profiles with the increasing temperatures. Furthermore, genetic analysis of the sxtA4 gene showed that greater genetic diversity—quantified by nucleotide diversity (π) ranging from 9.91 to 30.21 across strains—was positively correlated with this wider array of toxin analogs (Shannon’s diversity index; p < 0.0001). Conserved regions within the gene were identified, suggesting that these regions may play important structural or functional roles in the saxitoxin biosynthetic pathway. These findings highlight the role of temperature, genetic diversity, and sxtA4 conserved regions in influencing toxin production and profiles in Alexandrium. Further research into the genetic mechanisms underlying saxitoxin biosynthesis will improve our understanding of Alexandrium’s adaptability to changing temperatures. Such insights are essential for effective ecosystem management and safeguarding public health.11Nsciescopu
In silico analyses of Tfx family DNA-binding proteins as transcriptional regulators
No full textThe Tfx family proteins are transcriptional regulators that have an N-terminal DNA-binding helix-turn-helix (HTH) motif. So far, their functions have been identified in two key roles. First, they act as an activator that regulates the expression of the fmdECB operon, which encodes formyl-methanofuran dehydrogenase in Methanothermobacter thermautotrophicus (formerly known as Methanobacterium thermoformicicum). Second, they serve as a repressor that regulates the expression of the codh-mch-mnh3 gene cluster, which is involved in carbon monoxide oxidation and subsequent hydrogen gas production in the hyperthermophilic archaeon Thermococcus onnurineus NA1. To gain a better understanding of the Tfx family proteins in other species, various in silico analyses were conducted, including gene occurrence studies, phylogenetic analysis, gene cluster analysis, and predictions of the tertiary structure. Tfx family proteins are predominantly found in Archaea, particularly within the Euryarchaeota phylum, exhibiting conservation rates ranging from 0% to 87.8%, depending on the specific classes. Additionally, Tfx proteins are often located close to specific genes, which might be their regulatory targets. The Tfx protein from T. onnurineus NA1, known as EnfR, has been determined to possess an "eighth note" fold structure. Other homologous proteins also display this fold, although they differ in the lengths of their N-terminal or C-terminal extensions, as predicted by AlphaFold. Notably, three basic amino acids that function as DNA-binding residues are conserved across these proteins. This foundational study will provide valuable insights into the functional characterization of Tfx family proteins.1
A Study on the Improvement Directions of the Implementation System for Marine Contaminated Sediment Remediation Projects in Korea
No full textMarine contaminated sediments pose long-term risks to ecosystems, fisheries, and human health, requiring systematic national management. This study analyzes Korea’s remediation projects, focusing on their procedural and institutional structures. The analysis shows that current practices depend on fragmented criteria for site designation, exclusive reliance on state funding, dredging-centered methods without feasibility studies, and weak monitoring and performance evaluation. Comparative review of international cases provides useful insights: the U.S. CERCLA enforces the polluter-pays principle and risk-based reviews; Germany’s BBodSchG establishes shared liability for landowners and managers; Japan’s Minamata Bay remediation project combined strong governmental leadership with resident monitoring; and Canada’s Randle Reef project institutionalized joint financing and stakeholder participation. Based on these findings, this study suggests five key directions for Korea: (1) risk-based, multi-criteria site designation; (2) diversified financing with stakeholder participation; (3) feasibility-based technology selection beyond dredging; (4) KPI-driven monitoring and feedback; and (5) institutionalized governance and transparency. These reforms are expected to shift the current state-dominated system toward a more sustainable and participatory framework for marine sediment remediation projects.22Nkc
Striation-based beamforming for a ship of opportunity in shallow water
No full textCoherent multipath arrivals in oceanic waveguides generate complex interference patterns that degrade the performance of conventional beamforming (CBF) on horizontal arrays, often causing azimuthal bias and sidelobes—especially in the endfire direction. These limitations stem from grazing-angle multipath propagation in the vertical plane. As a physics-based alternative, this study proposes striation-based beamforming (SBF), which leverages the waveguide invariant. SBF consists of three steps: (1) estimating the time-domain Green's function of an unknown broadband source via ray-based blind deconvolution, (2) resampling this Green's function along striation slopes (relative frequency shifts) aligned to the first arrival, and (3) applying CBF to the resampled Green's function. Anchoring to the first arrival—corresponding to the minimum grazing angle—allows SBF to reduce azimuthal bias and sidelobes. This study also introduces a simplified variant, termed CB1, which applies CBF exclusively to the first arrival, bypassing the resampling step. CB1 offers substantial computational savings while achieving performance comparable to SBF. Experimental results using a bottom-mounted horizontal array confirm CB1's effectiveness in tracking the azimuth of a ship of opportunity in shallow water.11Nsciescopu