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Number of results: 12
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Abstract

One of the main causes of damage to weirs regulating the flow of water in canals is local erosion of the bottom and banks. This is mainly due to the excessive kinetic energy of the stream flow and the uneven volumetric distribution of the water flow rate at the end of the strengthening. Due to this, 35–40% of hydraulic structures fail prematurely. The aim of the research was to determine the parameters of the spatial hydraulic jump arising behind the hydrotechnical structure and the rapid expansion of the cross-section. The research showed that the hydraulic jump with a curved cylinder in the plan is a spatial form and not only dissipates the energy of the stream, but also acts as a diffuser. With the stream expansion angle values in the range of 7–10°, a highly turbulent flow remains, which still has high kinetic energy at a distance from the end of the structure. At an angle of 25–27°, the flow is smooth, the velocity distribution is uniform across the width of the channel. In some cases, the forced expansion of the cross-section at the outflow of the weir favours the energy dissipation and uniform flow velocity distribution.
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Authors and Affiliations

Zhuzbay Kassymbekov
1
Abai Shinibaev
1
Galimzhan Kassymbekov
1

  1. Satbayev University, Satpayev Str., 22, Almaty, 050013, Kazakhstan
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Abstract

News might trigger jump arrivals in financial time series. The “bad” news and “good” news seem to have distinct impact. In the research, a double exponential jump distribution is applied to model downward and upward jumps. Bayesian double exponential jump-diffusion model is proposed. Theorems stated in the paper enable estimation of the model’s parameters, detection of jumps and analysis of jump frequency. The methodology, founded upon the idea of latent variables, is illustrated with simulated data.

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Authors and Affiliations

Maciej Kostrzewski
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Abstract

In the paper we present and apply a Bayesian jump-diffusion model and stochastic volatility models with jumps. The problem of how to classify an observation as a result of a jump is addressed, under the Bayesian approach, by introducing latent variables. The empirical study is focused on the time series of gas forward contract prices and EUA futures prices. We analyse the frequency of jumps and relate the moments in which jumps occur to calendar effects or political and economic events and decisions. The calendar effects explain many jumps in gas contract prices. The single jump is identified in the EUA futures prices under the SV-type models. The jump is detected on the day the European Parliament voted against the European Commission’s proposal of backloading. The Bayesian results are compared with the outcomes of selected non-Bayesian techniques used for detecting jumps.

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Authors and Affiliations

Maciej Kostrzewski
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Abstract

Previous researchers have been widely studied the equation for calculating the energy dissipation in USBR Type IV, applied in the stilling basin structure as an energy dissipator. However, inefficient energy dissipating basins are commonly found in the field due to the large discharge and high water head, potentially damaging the bottom of the energy dissipating basin and its downstream river. Therefore, an energy dissipator plan fulfilling the safe specifications for the flow behaviour that occurred is required. This study aimed to determine the variation of the energy dissipators and evaluate their effect on the hydraulic jump and energy dissipation. For this purpose, a physical model was undertaken on the USBR Type IV spillway system. The novelty of this experiment showed that combination and modification dissipation features, such as floor elevation, end threshold and riprap lengthening, could effectively dissipate the impact of energy downstream. The final series exhibited a significantly higher Lj/y1 ratio, a favourable condition due to the compaction of the hydraulic jump. There was also a significant increase in the downstream tailwater depth (y2) during the jump formation. Therefore, the final series energy dissipator was better in the stilling basin design for hydraulic jump stability and compaction. The increase in energy dissipation for the final series type was the highest (98.4%) in Q2 and the lowest (84.8%) in Q10 compared to the original series. Therefore, this type can better reduce the cavitation risk damaging to the structure and downstream of the river.
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Authors and Affiliations

Alfiansyah Yulianur Bantacut
1
ORCID: ORCID
Azmeri Azmeri
1
ORCID: ORCID
Faris Zahran Jemi
2
ORCID: ORCID
Ziana Ziana
1
ORCID: ORCID
Muslem Muslem
1

  1. Universitas Syiah Kuala, Faculty of Engineering, Civil Engineering Department, Syech Abdur-Rauf No 7, Darussalam, 23111, Banda Aceh, Indonesia
  2. Universitas Syiah Kuala, Faculty of Engineering, Electrical Engineering Department, Banda Aceh, Indonesia
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Abstract

Energy dissipator functions to dissipate the river-flow energy to avoid longitudinal damage to the downstream river morphology. An optimal energy dissipator planning is essential to fulfilling safe specifications regarding flow behavior. This study aims to determine the variation of energy dissipators and evaluate its effect on the hydraulic jump and energy dissipation. For this purpose, a physical model was carried out on the existing weir condition (two steps). It was also carried out on four stepped-weir variations, i.e., three-step, three-step with additional baffle blocks at the end sills, four-step, and six-step. Dimensional analysis was employed to correlate the different parameters that affect the studied phenomenon. The study shows a three-step jump shows a significantly higher Lj/y1 ratio, which is an advantage to hydraulic jumps’ compaction. The comparison of energy dissipation in all weir variations shows that the three-stepped weir has wasted more energy than other types. The energy dissipation increase of the three-step type is 20.41% higher than the existing type’s energy dissipation and much higher than other types. The dimensions of the energy dissipation basin are the ratio of the width and height of the stairs (l/h) of the three-step type (2.50). Therefore, this type is more optimal to reduce the cavitation risk, which damages the river structure and downstream area.
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Bibliography

ABBASPOUR A., PARVINI S., DALIR A.H. 2016. Effect of buried plates on scour profilesdownstream of hydraulic jump in open channels with horizontal and reverse bed slopes. Water Science and Engineering. Vol. 9(4) p. 329–335. DOI 10.1016/j.wse.2017.01.003.

ABDEL AAL G.M., SOBEAH M., HELAL E., EL-FOOLY M. 2018. Improving energy dissipation on stepped spillways using breakers. Ain Shams Engineering Journal. Vol. 9(4) p. 1887–1896. DOI 10.1016/j.asej.2017.01.008.

ALAM R.R.R., TAUFIQ M. 2018. Kajian hidrolika pelimpah samping pada model fisik Bendungan Pasuruhan Kabupaten Magelang Provinsi Jawa Tengah dengan Skala 1:60 [Study of side spillway hydraulics on physical model of Pasuruan Reservoir, Magelang Regency, Central Java Province with a scale of 1:60]. Art. of MSc Thesis. Water Engineering, Engineering Faculty – Brawijaya University p. 1–9.

ALTALIB A.N., MOHAMMED A.Y., HAYAWI H.A. 2019. Hydraulic jump and energy dissipation downstream stepped weir. Flow Measurement and Instrumentation. Vol. 69, 101616. DOI 10.1016/j.flowmea-sinst.2019.101616.

AZMERI A., LEGOWO S., REZKYNA N. 2020. Interphase modeling of soil erosion hazard using a Geographic Information System and the Universal Soil Loss Equation. Journal of Chinese Soil and Water Conservation. Vol. 51(2) p. 65–75. DOI 10.29417/JCSWC.202006_51(2).0003.

BARANI G.A., RAHNAMA M.B., SOHRABIPOOR N. 2005. Investigation of flowenergy dissipation over different stepped spillways. American Journal of Applied Sciences. Vol. 2(6) p. 1101–1105. DOI 10.3844/ajassp.2005.1101.1105.

BASRI H., AZMERI A., WESLI W., JEMI F.Z. 2020. Simulation of sediment transport in Krueng Baro River, Indonesia, Jamba. Journal of Disaster Risk Studies. Vol. 12(1), a934 p. 1–9. DOI 10.4102/jamba.v12i1.934.

BEJESTAN M.S., NEISI K. 2009. A new roughened bed hydraulic jump stilling basin. Asian Journal of Applied Sciences. Vol. 2(5) p. 436– 445. DOI 10.3923/ajaps.2009.436.445.

CHANSON H. 1994. Comparison of energy dissipation between nappe and skimming flowregimes on stepped chutes. Journal of Hydraulic Reserch. Vol. 32(2) p. 213–218. DOI 10.1080/00221686.1994.10750036.

CHANSON H. 2009. Current knowledge in hydraulic jumps and related phenomena. A survey of experimental results. European Journal of Mechanics B/Fluids. Vol. 28(2) p. 191–210. DOI 10.1016/j.euromechflu.2008.06.004.

ELNIKHELY E.A. 2018. Investigation and analysis of scour downstream of a spillway, Ain Shams Engineering Journal. Vol. 9 (4) p. 2275– 2282. DOI 10.1016/j.asej.2017.03.008.

HUSAIN D., ALHAMID A.A., NEGM A.A.M. 2010. Length and depth of hydraulic jump in sloping channels. Journal of Hydraulic Research. Vol. 32(6) p. 899–910. DOI 10.1080/00221689409498697.

KARBASI M. 2016. Estimation of classical hydraulic jump length using teaching–learning based optimization algorithm. Journal of Materials and Environmental Science. Vol. 7(8) p. 2947–2954.

KIM Y., CHOI G., PARK H., BYEON S. 2015. Hydraulic jump and energy dissipation with sluice gate. Water. Vol. 7 p. 5115–5133. DOI 10.3390/w7095115.

LI L.X., LIAO H.S., LIU D., JIANG S.Y. 2015. Experimental investigation of the optimization of stilling basin with shallow-water cushion used for low Froude number energy dissipation. Journal of Hydrodinamics. Vol. 27(4) p. 552–529. DOI 10.1016/S1001-6058 (15)60512-1.

SULISTIONO B., MAKRUP L. 2017. Study of hydraulic jump length coefficient with the leap generation by canal gate model. American Journal of Civil Engineering. Vol. 5(3) p. 148–154. DOI 10.11648/j.ajce.20170503.14.

TIWARI H.L., GOEL A. 2016. Effect of impact wall on energy dissipation in stilling basin. KSCE Journal of Civil Engineering. DOI 10.1007/s12205-015-0292-5.

WÜTHRICH D., CHANSON H. 2014. Hydraulics, air entrainment, and energy dissipation on a gabion stepped weir. Journal of Hydraulic Engineering. Vol. 140(9) p. 04014046.1–04014046.10. DOI 10.1061/(ASCE)HY.1943-7900.0000919.
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Authors and Affiliations

Azmeri Azmeri
1
ORCID: ORCID
Hairul Basri
2
ORCID: ORCID
Alfiansyah Yulianur
1
ORCID: ORCID
Ziana Ziana
1
ORCID: ORCID
Faris Zahran Jemi
3
ORCID: ORCID
Ridha Aulia Rahmah
1

  1. Syiah Kuala University, Faculty of Engineering, Civil Engineering Department, Jl. Tgk. Syeh Abdul Rauf No. 7, Darussalam – Banda Aceh 23111, Indonesia
  2. Syiah Kuala University, Faculty of Agriculture, Department of Soil Science, Banda Aceh, Indonesia
  3. Syiah Kuala University, Faculty of Engineering, Department of Electrical Engineering, Banda Aceh, Indonesia
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Abstract

Day-boundary discontinuity (DBD) is an effect present in precise GNSS satellite orbit and clock products originating from the method used for orbit and clock determination. The non-Gaussian measurement noise and data processing in 24 h batches are responsible for DBDs. In the case of the clock product, DBD is a time jump in the boundary epochs of two adjacent batches of processed data and its magnitude might reach a couple of ns. This article presents the four GNSS (Global Navigation Satellite System) systems DBD analysis in terms of change over an 8 year period. For each of 118 satellites available in this period, the yearly value of DBD was subject to analysis including standard deviation and frequency of outliers. Results show that the smallest DBDs appear in the GPS system, the biggest – for the BeiDou space segment. Moreover, the phenomenon of changes in DBDs over time is clearly seen at the beginning of the analysed period when the magnitude and number of the DBDs were larger than for current, newest clock products
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Authors and Affiliations

Kamil Maciuk
1
Inese Varna
2
Jacek Kudrys
1

  1. Department of Integrated Geodesy and Cartography, AGH University, Mickiewicza Av. 30, 30-059 Krakow, Poland
  2. Institute of Geodesy and Geoinformatics, University of Latvia, Jelgavas St. 3, LV-1004, Riga, Latvia
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Abstract

In this paper a new method of frequency jumps detection in data from atomic clock comparisons is proposed. The presented approach is based on histogram analysis for different time intervals averaging phasetime data recorded over a certain period of time. Our method allows identification of multiple frequency jumps for long data series as well to almost real-time jump detection in combination with advanced filtering. Several methods of preliminary data processing have been tested (simple averaging, moving average and Vondrak filtration), to achieve flexibility in adjusting the algorithm parameters for current needs which is the key to its use in determining ensemble time scale or to control systems of physical time scales, such as UTC(PL). The best results have been achieved with the Vondrak filter.
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Authors and Affiliations

Michał Marszalec
1
Marzenna Lusawa
1
Tomasz Osuch
1 2

  1. National Institute of Telecommunications, Szachowa 1, 94-894 Warsaw, Poland
  2. Warsaw University of Technology, Faculty of Electronics and Information Technology, Institute of Electronic Systems, Nowowiejska 15/19, 00-665 Warsaw, Poland
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Abstract

This paper presents results of the study devoted to analysis of impact of upper extremities' momentum on the jump length and analysis of selected kinematic data changes during the standing long jump. Four young sportsmen participated in the initial study. They have performed standing long jump in two measuring conditions: with and without arms swinging. Motion was captured using a 3D opto-electronic camera system SMART (BTS) and selected kinematic data were evaluated using software packages and data processing: trajectory of body centre of gravity (COG), velocity of COG, maximal vertical distance of COG, take-off angle together with momentum of upper extremities were analyzed. The data were statistically evaluated using descriptive statistics and analysis of variance. Statistical significance of the kinematic data and jump length were analyzed using the Kruskal-Wallis test and post-hoc test (p<0.05) in Statistics toolbox of Matlab program. Statistically significant differences were assessed within intraindividual and intraclass comparison of data.

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Authors and Affiliations

Lenka Szerdiová
Dušan Simšik
Zlatica Dolná
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Abstract

Second law analysis (entropy generation) for the steady two-dimensional laminar forced convection flow, heat and mass transfer of an incompressible viscous fluid past a nonlinearly stretching porous (permeable) wedge is numerically studied. The effects of viscous dissipation, temperature jump, and first-order chemical reaction on the flow over the wedge are also considered. The governing boundary layer equations for mass, momentum, energy and concentration are transformed using suitable similarity transformations to three nonlinear ordinary differential equations (ODEs). Then, the ODEs are solved by using a Keller’s box algorithm. The effects of various controlling parameters such as wedge angle parameter, velocity ratio parameter, suction/injection parameter, Prandtl number, Eckert number, temperature jump parameter, Schmidt number, and reaction rate parameter on dimensionless velocity, temperature, concentration, entropy generation number, and Bejan number are shown in graphs and analyzed. The results reveal that the entropy generation number increases with the increase of wedge angle parameter, while it decreases with the increase of velocity ratio parameter. Also, in order to validate the obtained numerical results of the present work, comparisons are made with the available results in the literature as special cases, and the results are found to be in a very good agreement.

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Authors and Affiliations

Nemat Dalir
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Abstract

A Bayesian stochastic volatility model with a leverage effect, normal errors and jump component with the double exponential distribution of a jump value is proposed. The ready to use Gibbs sampler is presented, which enables one to conduct statistical inference. In the empirical study, the SVLEDEJ model is applied to model logarithmic growth rates of one month forward gas prices. The results reveal an important role of both jump and stochastic volatility components.

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Authors and Affiliations

Maciej Kostrzewski
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Abstract

The stability and positivity of linear positive Markovian jump systems with respect to part of the variables is considered. The methodologies of stability of positive systems with known transition probabilities based on common linear copositive Lyapunov function and stability of linear systems with respect to part of the variables are combined to find sufficient conditions of the stochastic stability and positivity of Markovian jump systems with respect to part of the variables. The results are extended for a class of nonlinear positive Markovian jump systems with respect to part of the variables. An example is given to illustrate the obtained results.

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Authors and Affiliations

L. Socha
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Abstract

In thermos fluid dynamics, free convection flows external to different geometries, such as cylinders, ellipses, spheres, curved walls, wavy plates, cones, etc., play major role in various industrial and process engineering systems. The thermal buoyancy force associated with natural convection flows can play a critical role in determining skin friction and heat transfer rates at the boundary. In thermal engineering, natural convection flows from cylindrical bodies has gained exceptional interest. In this article, we mathematically evaluate an entropy analysis of magnetohydrodynamic third-grade convection flows from permeable cylinder considering velocity and thermal slip effects. The resulting non-linear coupled partial differential conservation equations with associated boundary conditions are solved with an efficient unconditionally stable implicit finite difference Keller-Box technique. The impacts of momentum and heat transport coefficients, entropy generation and Bejan number are computed for several values of non-dimensional parameters arising in the flow equations. Streamlines are plotted to analyze the heat transport process in a two-dimensional domain. Furthermore, the deviations of the flow variables are compared with those computed for a Newtonian fluid and this has important implications in industrial thermal material processing operations, aviation technology, different enterprises, energy systems and thermal enhancement of industrial flow processes.
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Authors and Affiliations

K. Madhavi
V. Ramachandra Prasad
S. Abdul Gaffar
K. Venkatadri

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