scholarly journals A routing-benefited deployment approach combining static and dynamic layouts for underwater optical wireless networks

2021 ◽  
Vol 17 (2) ◽  
pp. 155014772199961
Author(s):  
Zhongwei Shen ◽  
Hongxi Yin ◽  
Yanjun Liang ◽  
Rigele Maao ◽  
Lianyou Jing
Keyword(s):  
Optical Communication ◽  
Loss Rate ◽  
Communication Model ◽  
Optical Wireless ◽  
Wireless Optical Communication ◽  
Area Of Interest ◽  
Virtual Force ◽  
The Impact ◽  
Term Monitoring

A routing-benefited deployment algorithm combining static and dynamic layouts is proposed, and its comprehensive performance evaluation is given in this article. The proposed routing-benefited deployment algorithm is intended to provide a suitable network deployment and subsequent data transmission approach for underwater optical networking and communication. Static nodes are anchored for long-term monitoring, and movable nodes can adjust their depths based on the virtual force and move with the variation of area-of-interest changing. Then, nodes begin to collect data that they can monitor and transmit to sink nodes. Here, the underwater wireless optical communication model is described to actualize the real environment, and the vector-based forwarding protocol is particularly considered to compare the impact of different deployment algorithms on routing. It is shown by simulation experiment results that routing-benefited deployment algorithm outperforms several existing traditional virtual force deployment algorithms in terms of coverage, lifetime, energy consumption balance, packet-loss rate, and time-delay.

scholarly journals Performance Evaluation of Underwater Wireless Optical Communication System by Varying the Environmental Parameters

Photonics ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 74
Author(s):  
Dong-Chang Li ◽  
Chia-Chun Chen ◽  
Shien-Kuei Liaw ◽  
Shofuro Afifah ◽  
Jiun-Yu Sung ◽  
...  
Keyword(s):  
Optical Communication ◽  
Environmental Parameters ◽  
Artificial Seawater ◽  
Blue Laser ◽  
Laser Source ◽  
Water Tank ◽  
Wireless Optical Communication ◽  
Transmission Distance ◽  
Flow Turbulence ◽  
The Impact

Underwater wireless optical communication (UWOC) has been considered a promising technology for high-speed underwater transmission. Some Gb/s level UWOC systems applying visible light have been demonstrated with a transmission distance of several meters or more. Many of the previous works focus on the advanced technologies to push the systems’ capacity–distance performance. However, practical environmental factors issue such as flow turbulence and temperature variation are seldom studied through specific statistical/theoretical models. In this paper, a UWOC system using a 450 nm blue light laser source was set up using a 1.5-m water tank with mirrors located on both sides for single or multiple reflections corresponding to different transmission distances. The blue laser was modulated by a 1.25 Gbps NRZ-OOK format with PRBS of 7, 24 or 31, respectively, for system performance comparison. The bit error rate (BER) values were measured in 1.5, 3.0 and 6 m, respectively, for system evaluation. At room temperature, the BER value was down to 10 × 10−8 for a 1.25 Gbps data rate in a 6 m transmission. Then, the UWOC transmission system experiment was carried out under several environmental parameters such as temperature, turbulence, artificial seawater by adding salt to simulate practical application in river or sea. When a submerged motor with an output of 1200 L/h was used as a water flow turbulence source, the impact to BER and transmission quality was negligible. For the temperature change issue, the experiment shows that around the original temperature of 25 °C had the best BER as compared to other temperature ranges from 10 to 50 °C. For artificial seawater issues by adding salt to simulate the real seawater environment. The transmission distance was only 3-m instead of 6 m, mainly due to particle scattering and water disturbance. With the motor pump on, the power penalty was 1 dB at 10 × 10−8 BER when compared to the motor pump off.

Temporal changes in an alligator snapping turtle (Macrochelys temminckii) population

2013 ◽  
Vol 40 (1) ◽  
pp. 77 ◽  
Author(s):  
Mitchell B. East ◽  
J. Daren Riedle ◽  
Day B. Ligon
Keyword(s):  
Management Practices ◽  
Unknown Origin ◽  
Current Status ◽  
Macrochelys Temminckii ◽  
The Status ◽  
Management Recommendations ◽  
The Impact ◽  
Term Monitoring ◽  
Term Data

Context Monitoring populations of long-lived species requires continuous long-term efforts. This is especially applicable for species that have experienced declines range-wide. Aims Our study assessed the current status of a population of wild Macrochelys temminckii and compared the present results to those from a survey conducted nearly a decade ago. Methods Trapping in 2010–2011 was conducted on two creeks within the refuge, during the months of May–July. Capture data were compared with data collected by similar methods in 1997–2001. Key results The population structure of M. temminckii was dominated by juveniles, with few large adults or small juveniles detected and a missing size class was evident. Retrospective analysis of 1997–2001 data revealed that the population was likely to be in decline even then, despite high capture rates. Conclusions The M. temminckii population showed significant declines that indicated that the population had experienced stressors of unknown origin. The status of M. temminckii at the refuge is concerning, given the protection afforded this remnant population. Implications Short-term data from 1997–2001 indicated a healthy M. temminckii population, whereas longer-term data showed that the population has declined, resulting in significant demographic changes. Continued monitoring will be necessary to develop management recommendations and track the impact of implemented management practices. Longer-term monitoring of long-lived vertebrates is required to identify population trends.

scholarly journals Monitoring Selected Species of Mammals in Grand Teton National Park in 2001

2001 ◽  
Vol 25 ◽  
pp. 82-87
Author(s):  
Brian Miller ◽  
Hank Harlow
Keyword(s):  
National Park ◽  
Vegetation Type ◽  
Vegetation Types ◽  
Population Composition ◽  
Grand Teton National Park ◽  
Needed Information ◽  
Mammal Distribution ◽  
The Impact ◽  
Term Monitoring

Our objective is to establish a long-term monitoring project that will assess the abundance and densities of selected species of mammals at sites representing five defined vegetation types found in Grand Teton National Park. The term monitoring implies data collection over multiple years. Taking long term estimations of population composition before, during, and after biotic and abiotic changes provides needed information to assess the impacts of such changes and furnish useful options for management decisions. This standardized monitoring plan will provide information on small and medium-sized mammals that will (1) assess species use of habitat, (2) monitor changes in species composition as a result of environmental change, such as precipitation and temperature, (3) produce predictive models of small and medium-sized mammal distribution based on vegetation type, and (4) analyze the impact of wolf colonization on the mammal (and plant) community.

Changes Over Time

2018 ◽  
pp. 283-305 ◽  
Author(s):  
Peter A. Gell ◽  
Marie-Elodie Perga ◽  
C. Max Finlayson
Keyword(s):  
Data Sets ◽  
Lake Ecosystems ◽  
Wetland Ecosystems ◽  
Sediment Layers ◽  
Time Frames ◽  
Changes Over Time ◽  
The Impact ◽  
Term Monitoring ◽  
Term Data

Freshwater systems are continuously shaped by cyclical and directional forces of change, whether they be natural or anthropogenic. Beyond gradual transitions disturbances can reset their internal dynamics generating an abrupt ecological shift. Long-term data sets of gradual or abrupt change can be accessed by exhuming the physical, chemical, and biological remains archived in the sediment layers within lakes and wetlands. Long-term monitoring programmes offer more detailed evidence, usually over shorter time frames. In combination these records attest to the response of wetlands to climate and the impact of industrialised people. Humans have modified lake ecosystems for millennia and the condition of many wetland ecosystems have changed such that they are now regarded as novel. Long-term records provide targets for wetland restoration and can identify the main drivers of degradation. Identification of the character of modern Ramsar wetlands may be enhanced by reference to records of past state.

scholarly journals Analysis of the scores of competency test

2018 ◽  
Vol 210 ◽  
pp. 04006
Author(s):  
Jana Pasáčková
Keyword(s):  
Czech Republic ◽  
Secondary Schools ◽  
The Czech Republic ◽  
Study Programme ◽  
Level Of Knowledge ◽  
Long Term Monitoring ◽  
The University ◽  
The Impact ◽  
Term Monitoring

Since decreasing level of knowledge of mathematics is the problem at universities, not only in the Czech Republic, we try to define some reasons for that between our students from different secondary schools. The paper discusses the results of the examinations in mathematics at the university in the Czech Republic. The aim is focused on the differences between the scores of students from different secondary schools. We compare the results of two tests which students have to pass during the semester. In addition, we compare the impact of introducing a new subject called “Math seminar”. This seminar should help students to complete their knowledge of topics from mathematics of secondary schools. We observe the improvement of students who passed the Math seminar. We observe the impact of passing the school-leaving exam from mathematics as well. We would like to consider this as a part of a long-term monitoring of students in this study programme and re-analyze unsuccessful students after they pass the course “Math seminar”.

Fire and its impact on avian population dynamics

1997 ◽  
Vol 3 (3) ◽  
pp. 206 ◽  
Author(s):  
G. Barry Baker ◽  
E. Belinda Dettmann ◽  
Stephen J. Wilson
Keyword(s):  
Population Size ◽  
Fire Regimes ◽  
Long Term Study ◽  
Sclerophyll Forest ◽  
In Fire ◽  
Avian Populations ◽  
The Impact ◽  
Term Monitoring ◽  
Probability Of Capture

Survival rate, population size, recruitment and probability of capture, derived from a long-term study of 20 passerine species in wet sclerophyll forest near Canberra, were used to measure the impact of a high intensity wildfire which burnt 70% of the study area. The wildfire significantly affected the population size of 13 species for a period of up to six years following the fire. Survival and recruitment were the least sensitive measures of impact and indicated a significant response to fire for only 2 of 10 species. We detected measurable effects of the fire for 17 of the 20 species studied. Many of these species had returned to prefire levels within three years, but for nine species the effects were still apparent six years later. Mark-recapture methodology provides an effective way of measuring the impact of fire regimes in forest environments. Long-term monitoring programmes should be established in fire-prone forest environments to contribute toward our understanding of fire, and its effect on avian populations. Such programmes have resource implications and researchers are urged to encourage the participation of the amateur bird banding community to contribute to such projects.

Experimental Analysis of the Impact on the Durability of Concrete Additions

2016 ◽  
Vol 249 ◽  
pp. 73-78 ◽  
Author(s):  
Vladimír Suchánek ◽  
Kateřina Hájková
Keyword(s):  
Free Fall ◽  
Concrete Surface ◽  
Hardened Concrete ◽  
Concrete Mixer ◽  
Long Term Monitoring ◽  
The Impact ◽  
Term Monitoring ◽  
Furnace Slag

This report deals with long term monitoring of durability properties of concrete using different weight doses of various kinds of additions. Particularly limestone, silica fume as a 50% suspension and blast furnace slag were used. Even though the basic recipe is based on the designed concrete, all the fresh concrete was made with a free-fall concrete mixer in the laboratory. This report deals with long-term monitoring of cement concrete surface resistance to water and defrosting chemicals (achieved 475 cycles). The article also describes results of following tests: determination of concrete frost resistance, depth of water penetration under pressure and depth of chloride penetration. Standard tests of fresh and hardened concrete specimens complement the experiment.

scholarly journals Design of Low Power Hybrid Communication Model

2021 ◽  
Author(s):  
Menaka D ◽  
Sabitha Gauni ◽  
Manimegalai C.T ◽  
Kalimuthu K
Keyword(s):  
Optical Communication ◽  
Data Transmission ◽  
Weather Conditions ◽  
Communication Model ◽  
Underwater Communication ◽  
Long Distance ◽  
Weather Forecasts ◽  
High Data ◽  
Military Equipment ◽  
Wireless Optical Communication

Abstract Communication in underwater is a growing research topic that plays a big role in forecasting accurate weather conditions. In which Acoustic communication is the upcoming technology well qualified for its long-distance underwater communication with certain restrictions like low data rate and high latency. To overcome this constrain wireless optical communication are preferred for high data transmission and less delay. The attempts are made to analyze the performance of the turbid and coastal water conditions.To improve the underwater communication model,a hybrid model is proposed for the applications like weather forecasts, military equipment, and missing debris.

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