A Feasibility Investigation for Developing Artificial Beachrocks: A Potential Measure for Coastal Protection in Southeast Yogyakarta Coast, Indonesia

<p>Erosion prone sandy beaches are frequently covered by cement and mortar to preserve the coastal zone, but the conventional approach has an adverse impact on the environment, altering the coastal landscape and processes unfavorably. The term &#8220;beachrock&#8221; refers to cemented coastal sediments through a long-term formation of CaCO<sub>3</sub> cement, and which is an important feature in many tropical coastlines as it appears to have a substantial anchoring effect against wave effects and erodibility. Therefore, the objective of this study is to evaluate the feasibility in progressing the formation of artificial beachrocks using natural materials (e.g., microbes, sand, shell, pieces of coral, and seaweed etc.) within a short-term, and to introduce the method as a novel candidate for coastal protection. In this study, both resistivity survey and multi analysis seismic wave (MASW) survey along the same lines were performed at first to elucidate the subsurface structure of existing beachrocks in the Southeast Yogyakarta coastal area (Indonesia), followed by the laboratory analysis, which is aimed understand the basics in the formation mechanism. Peloidal micrite cement, the cement comprised of aragonite needles, micritized granules and the cover of micritic were observed in natural beachrocks. Mimicking the mechanism, an attempt has been undertaken to develop artificial beachrocks in the laboratory via microbial induced carbonate precipitation (MICP). Finally, the physical and mechanical properties were well compared between the artificially formed beachrocks and natural beachrocks collected from the survey lines. The results suggest that the artificial deposits treated for 14 days under optimum conditions, achieved a peak unconfined compressive strength of around 6 MPa similar to that of weak-consolidated natural beachrock. The comparison further reveals that the variables such as porosity, Vp, Vs, and strength are primarily rely on the precipitated morphology of the crystals.</p>

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Simulations of Shoreline Changes along the Delaware Coast

10.21079/11681/39559 ◽

2021 ◽

Author(s):

Yan Ding ◽

Sung-Chan Kim ◽

Rusty L. Permenter ◽

Richard B. Styles ◽

Jeffery A. Gebert

Keyword(s):

Sediment Transport ◽

Coastal Sediments ◽

Coastal Protection ◽

Shoreline Evolution ◽

Longshore Sediment Transport ◽

Technical Report ◽

Indian River ◽

Sediment Transfer ◽

Island Coast

This technical report presents two applications of the GenCade model to simulate long-term shoreline evolution along the Delaware Coast driven by waves, inlet sediment transport, and longshore sediment transport. The simulations also include coastal protection practices such as periodic beach fills, post-storm nourishment, and sand bypassing. Two site-specific GenCade models were developed: one is for the coasts adjacent to the Indian River Inlet (IRI) and another is for Fenwick Island. In the first model, the sediment exchanges among the shoals and bars of the inlet were simulated by the Inlet Reservoir Model (IRM) in the GenCade. An inlet sediment transfer factor (γ) was derived from the IRM to quantify the capability of inlet sediment bypassing, measured by a rate of longshore sediments transferred across an inlet from the updrift side to the downdrift side. The second model for the Fenwick Island coast was validated by simulating an 11-y ear-long shoreline evolution driven by longshore sediment transport and periodic beach fills. Validation of the two models was achieved through evaluating statistical errors of simulations. The effects of the sand bypassing operation across the IRI and the beach fills in Fenwick Island were examined by comparing simulation results with and without those protection practices. Results of the study will benefit planning and management of coastal sediments at the sites.

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ANALYTICAL MODELLING OF CONCRETE LONG-TERM AND SHORT-TERM STRAIN/BETONO TRUMPALAIKIŲ IR ILGALAIKIŲ DEFORMACIJŲ ANALITINIS MODELIAVIMAS

Journal of Civil Engineering and Management ◽

10.3846/13921525.2001.10531693 ◽

2001 ◽

Vol 7 (1) ◽

pp. 15-22

Author(s):

Mindaugas Augonis

Keyword(s):

Experimental Data ◽

Mechanical Properties ◽

Differential Equations ◽

Present Model ◽

Coarse Aggregate ◽

Physical And Mechanical Properties ◽

Homogeneous Material ◽

Stress And Strain ◽

Short Term

Concrete is not a homogeneous material. However, such an approach does not enable one to precisely determine short-term or long-term strain of concrete which consists of separate materials components with different physical and mechanical properties. Therefore, concrete should be considered a composite of coarse aggregate and mortar. Such a model enables one to take into account different properties of concrete components. The creep or shrinkage of coarse aggregate can be assumed as zero. It is enough to accept only creep or shrinkage of mortar and the present model becomes simpler. In case of a long term, load stress in matrix decreases because of relaxation. Thus, part of load passes from matrix to coarse aggregate. In order to describe such a phenomenon by integro-differential equations of creep it is necessary to know stress history for each element of matrix. It would be difficult to determine creep in this way. It is by far easier to solve macromechanical model of creep by the method of effective modulus of ageing material developed by Z. P. Bazant. This method requires only the increments of stress and strain. Figs 6 and 9–12 show that present models give similar results which are quite well-coincident with present experimental data.

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Long-Term Extreme Response of Marine Structures Considering the Combination of First and Second Order Wave Effects

Volume 2B: Structures, Safety and Reliability ◽

10.1115/omae2013-11127 ◽

2013 ◽

Author(s):

Luis Volnei Sudati Sagrilo ◽

Fernando Jorge Mendes de Sousa ◽

José Antonio Vargas Bazán ◽

Zhen Gao ◽

Arvid Naess

Keyword(s):

Hermite Polynomials ◽

Second Order ◽

Short Term ◽

Marine Structure ◽

Slow Drift ◽

Extreme Response ◽

Wave Effects ◽

Speed Up ◽

Non Gaussian

In this paper, the long-term extreme response of a floating marine structure subjected to first and second order (slow-drift) wave effects is addressed. The proposed formulation is based on the long-term up-crossing rate, which is obtained by integrating the contribution of all short-term sea states. In order to speed up the evaluation of the long-term integral, an analytical expression for the short-term responses up-crossing rates was adopted. This expression is based on Hermite polynomials, and considers the response as a second order Volterra stochastic process. This formulation was applied to evaluate the 1-yr, 10-yr and 100-yr lateral motions of a circular-shaped monocolumn platform, and the non-Gaussian (nonlinear) results are compared with those obtained by assuming the response as a Gaussian process.

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Modelling Cross-Shore Shoreline Change on Multiple Timescales and Their Interactions

Journal of Marine Science and Engineering ◽

10.3390/jmse9060582 ◽

2021 ◽

Vol 9 (6) ◽

pp. 582

Author(s):

Rob Schepper ◽

Rafael Almar ◽

Erwin Bergsma ◽

Sierd de de Vries ◽

Ad Reniers ◽

...

Keyword(s):

Shoreline Change ◽

Sandy Beaches ◽

Data Driven ◽

Short Term ◽

New Approach ◽

Multiple Timescales ◽

Direct Forcing ◽

Shoreline Prediction ◽

Study Sites

In this paper, a new approach to model wave-driven, cross-shore shoreline change incorporating multiple timescales is introduced. As a base, we use the equilibrium shoreline prediction model ShoreFor that accounts for a single timescale only. High-resolution shoreline data collected at three distinctly different study sites is used to train the new data-driven model. In addition to the direct forcing approach used in most models, here two additional terms are introduced: a time-upscaling and a time-downscaling term. The upscaling term accounts for the persistent effect of short-term events, such as storms, on the shoreline position. The downscaling term accounts for the effect of long-term shoreline modulations, caused by, for example, climate variability, on shorter event impacts. The multi-timescale model shows improvement compared to the original ShoreFor model (a normalized mean square error improvement during validation of 18 to 59%) at the three contrasted sandy beaches. Moreover, it gains insight in the various timescales (storms to inter-annual) and reveals their interactions that cause shoreline change. We find that extreme forcing events have a persistent shoreline impact and cause 57–73% of the shoreline variability at the three sites. Moreover, long-term shoreline trends affect short-term forcing event impacts and determine 20–27% of the shoreline variability.

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Conceptual short-term memory (CSTM) supports core claims of Christiansen and Chater

Behavioral and Brain Sciences ◽

10.1017/s0140525x15000928 ◽

2016 ◽

Vol 39 ◽

Author(s):

Mary C. Potter

Keyword(s):

Working Memory ◽

Rapid Serial Visual Presentation ◽

Language Comprehension ◽

Short Term Memory ◽

Visual Presentation ◽

Long Term Memory ◽

Short Term ◽

Term Memory ◽

Use Of Knowledge

AbstractRapid serial visual presentation (RSVP) of words or pictured scenes provides evidence for a large-capacity conceptual short-term memory (CSTM) that momentarily provides rich associated material from long-term memory, permitting rapid chunking (Potter 1993; 2009; 2012). In perception of scenes as well as language comprehension, we make use of knowledge that briefly exceeds the supposed limits of working memory.

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Ultrastructural investigations of MDL 19,660-induced effects on the canine platelet and megakaryocyte

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100159412 ◽

1990 ◽

Vol 48 (3) ◽

pp. 374-375

Author(s):

D.E. Loudy ◽

J. Sprinkle-Cavallo ◽

J.T. Yarrington ◽

F.Y. Thompson ◽

J.P. Gibson

Keyword(s):

Antidepressant Drug ◽

Beagle Dogs ◽

Long Term Effects ◽

Short Term ◽

Platelet Counts ◽

Toxicological Studies ◽

Induced Aggregation ◽

Internal Architecture

Previous short term toxicological studies of one to two weeks duration have demonstrated that MDL 19,660 (5-(4-chlorophenyl)-2,4-dihydro-2,4-dimethyl-3Hl, 2,4-triazole-3-thione), an antidepressant drug, causes a dose-related thrombocytopenia in dogs. Platelet counts started to decline after two days of dosing with 30 mg/kg/day and continued to decrease to their lowest levels by 5-7 days. The loss in platelets was primarily of the small discoid subpopulation. In vitro studies have also indicated that MDL 19,660: does not spontaneously aggregate canine platelets and has moderate antiaggregating properties by inhibiting ADP-induced aggregation. The objectives of the present investigation of MDL 19,660 were to evaluate ultrastructurally long term effects on platelet internal architecture and changes in subpopulations of platelets and megakaryocytes.Nine male and nine female beagle dogs were divided equally into three groups and were administered orally 0, 15, or 30 mg/kg/day of MDL 19,660 for three months. Compared to a control platelet range of 353,000- 452,000/μl, a doserelated thrombocytopenia reached a maximum severity of an average of 135,000/μl for the 15 mg/kg/day dogs after two weeks and 81,000/μl for the 30 mg/kg/day dogs after one week.

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Comparison of Auditory, Language, Memory, and Attention Abilities in Children With and Without Listening Difficulties

American Journal of Audiology ◽

10.1044/2020_aja-20-00018 ◽

2020 ◽

Vol 29 (4) ◽

pp. 710-727

Author(s):

Beula M. Magimairaj ◽

Naveen K. Nagaraj ◽

Alexander V. Sergeev ◽

Natalie J. Benafield

Keyword(s):

Auditory Processing ◽

Short Term Memory ◽

Group Differences ◽

Long Term Memory ◽

Short Term ◽

Significant Group ◽

Term Memory ◽

Memory And Attention ◽

Speed And Accuracy

Objectives School-age children with and without parent-reported listening difficulties (LiD) were compared on auditory processing, language, memory, and attention abilities. The objective was to extend what is known so far in the literature about children with LiD by using multiple measures and selective novel measures across the above areas. Design Twenty-six children who were reported by their parents as having LiD and 26 age-matched typically developing children completed clinical tests of auditory processing and multiple measures of language, attention, and memory. All children had normal-range pure-tone hearing thresholds bilaterally. Group differences were examined. Results In addition to significantly poorer speech-perception-in-noise scores, children with LiD had reduced speed and accuracy of word retrieval from long-term memory, poorer short-term memory, sentence recall, and inferencing ability. Statistically significant group differences were of moderate effect size; however, standard test scores of children with LiD were not clinically poor. No statistically significant group differences were observed in attention, working memory capacity, vocabulary, and nonverbal IQ. Conclusions Mild signal-to-noise ratio loss, as reflected by the group mean of children with LiD, supported the children's functional listening problems. In addition, children's relative weakness in select areas of language performance, short-term memory, and long-term memory lexical retrieval speed and accuracy added to previous research on evidence-based areas that need to be evaluated in children with LiD who almost always have heterogenous profiles. Importantly, the functional difficulties faced by children with LiD in relation to their test results indicated, to some extent, that commonly used assessments may not be adequately capturing the children's listening challenges. Supplemental Material https://doi.org/10.23641/asha.12808607

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