SELECTED
PAPER
ABSTRACTS
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MODEL
STUDIES FOR INTAKE AND OUTFALL SYSTEM OF L
K Ghosh, Additional Director, V
V Vaze, Chief Research Officer, ABSTRACT Tamil
Nadu Electricity Board (TNEB) has two power stations located at Ennore,
about 15 km North of Chennai. One is Ennore Thermal Power Station (ETPS)
and the other is North Chennai Thermal Power Station (NCTPS). Both the
power stations are operating on once through cooling water system and are
drawing required cooling water from Ennore creek. However, due to frequent
choking of creek mouth, both power stations are experiencing acute
shortage of the requisite coolant water. In order to suggest the remedial
measure to improve the conditions the studies were carried out for five
different alternative locations of intake and outfall on a physical
thermal model, constructed to the scales 1:360 (Horizontal) and 1:80
(Vertical). The recommended intake-outfall system obtained from Physical
model was tested on 1D mathematical model capable of simulating tidal
exchange and flow field considering discharge and withawal from power
plants. The results revealed that surface heat loss played dominant role
in reduction of temperature. The optimum area of Ennore creek mouth to be
maintained is 50 sq. m for effective utilization of tidal water by both
the power plants and it is found that the withdrawal of cooling water from
the port basin and discharge of warm water from NCTPS at Ennore creek near
the mouth is the most suitable solution for supplying cooling water for
both the power plants. Nature
Environment and Pollution Technology
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AUGMENTATION
OF WATER RESOURCES AT WELLINGTON, TAMIL NADU – R S Ramteke, Chief Research Officer, K Venugopal, Chief Research OfficerN Ghosh, Additional Director and G A Panvalkar, Asstt Research Officer ABSTRACT A
12 m high and 112 m long earthen dam was proposed to be constructed for
augmenting surface water resources at Wellington, Coonoor district,
Tamilnadu. For designing the
foundation, the quality of sub surface formation was to be assessed and
the geologically weak structures were to be delineated. As the topography of the area is not plane and also as thick
lateritic formations are
capping the deep-seated charnockite (bed rock), use of two different
geophysical methods viz. 1. Seismic Refraction and 2. Electrical
Resistivity, was necessitated. The results of these two geophysical
surveys have been integrated while characterizing the foundation. Two
continuous seismic profiles along the proposed dam axis and four vertical
electrical soundings in its reservoir bed were taken.
The results revealed a four-layered stratum.
The compressional wave velocities vary from 330 m/sec to 3345 m/sec
and the resistivities from 22 ohm-m to 907 ohm-m.
The low velocity and resistivity values (330 m/sec and 22 ohm-m
respectively) are attributed
to a loose and soft formation and their higher values (3345 m/sec and 907
ohm-m respectively) are attributed to a compact and hard formation.
The depths of different geological layers obtained from these
results were also co-related well with the borehole litho-logs.
No geologically weak structures have been identified in the area by
these investigations. The
presence of compact formation and the absence of geologically weak
structures at the site are favourable for founding the proposed structure. Indian Society for Hydraulics, Journal of Hydraulic Engineering,
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THE
STATE OF THE ART IN SEISMIC HAZARD ANALYSIS I
D Gupta , Joint Director ABSTRACT The
seismic hazard analysis is concerned with getting an estimate of the
strong-motion parameters at a site for the purpose of earthquake resistant
design or seismic safety assessment.
For generalized applications, seismic hazard analysis can also be
used to prepare macro or micro zoning maps of an area by
estimating the strong-motion parameters for a closely spaced grid of
sites. Two basic
methodologies used for the purpose are the “deterministic” and the
probabilistic” seismic hazard analysis (PSHA) approaches.
In the deterministic approach, the strong-motion parameters are
estimated for the maximum credible earthquake, assumed to occur at the
closest possible distance from the site of interest, without considering
the likelihood of its occurrence during a specified exposure period.
On the other hand, the probabilistic approach integrates the
effects of all the earthquakes expected to occur at different locations
during a specified life period, with the associated uncertainties and
randomness taken into account. The present paper gives a critical and detailed description
of both deterministic and probabilistic approaches for seismic hazard
analyses. A large number of
example results are presented to illustrate the implementations of the two
approaches. The results of the probabilistic approach are able to account
for the effects of all the controlling factors in a balanced way, and can
thus be considered more reliable. The
advantages quoted in favour of using the deterministic approach can simply
be achieved via de-aggregation of the probabilistic hazard analysis. ISET
Journal of Earthquake Technology, Paper No.428, Vol. 39, No.4
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GEOPHYSICAL
SURVEY FOR DELINEATION OF SEEPAGE R
S Ramteke, Chief Research Officer ABSTRACT The
Dyke No.1 of Dharoi Project, Gujarat was constructed on a stream which was
also bunded up earlier on the downstream of the dyke known as old babsar
Tank. Excessive seepage was noticed at downstream toe of the dyke which
continued even after the construction of loading berm and partly grouting
the foundation through the bottom of the cut off trench (COT).
A geophysical survey, comprising seismic refraction and Electrical
resistivity soundings and profiling was carried out to delineate the zones
that are prone to excessive seepage so that suitable remedial measures
could be adopted. Three
underwater seismic profiles and one continuous land profile were taken
parallel to the dyke axis. Four
electrical resistivity soundings and two profilings were also conducted.
The results of seismic survey indicated the presence of low
velocity zones below the bed level of COT.
These zones were also identified by the electrical resistivity
results and it appears to be continuous from the downstream toe of dyke to
the Babsar Tank. It was
inferred that these weak zones in the bedrock may be responsible for the
observed seepage. Journal
of Geophysics
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RESTORATION
OF THE DAMAGED RUNNER CHAMBERS BY EPOXY APPLICATION A
K Sathe, Senior Research Officer, V T Desai, Research Officer & A V
Patil, Asstt Research Officer ABSTRACT Reduction
in the thickness, followed by pitting of the surface and subsequent
cracking of the liner are the common distress phenomena observed in power
plant operation. The
probable reasons for these damages appear to be erosion due to silt laden
high velocity flow of water and/or cavitation, and existence of hair line
gap/pockets between steel and supporting concrete. This leads to non-monolithic action of liner and concrete.
The situation becomes worst when liner plates break into pieces
exposing the supporting concrete to high velocity flow.
Concrete erodes at much faster rate and forms cavities behind the
liner. The damaged runner
chamber ultimately brings
about the total breakdown of the power unit stopping power generation and
causing huge loss of revenue. Such
damaged runner chamber either needs replacement of the liner or repairs to
put the unit in operation. Similar
situations were encountered at Chilla and Chiplima power house.
The conventional measures adopted for repairs did not perform
satisfactorily with the result the state of distress continued.
These damaged runner chambers were restored successfully by epoxy
application. The methodology
adopted was found to be lasting and durable.
This paper deals with three case studies and describes the approach
and methodology suggested by CWPRS and finally adopted for restoration
along with pre application studies on epoxy compounds. NBM
& CW October,2003.
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ESTIMATION
OF TEMPERATURE RISE IN MASS CONCRETE PLACED IN LIFTS USING COMPUTER
PROGRAM
V
T Desai, Research Officer, A V Patil, Assistant Research Officer
& ABSTRACT Excessive
temperature rise in mass concrete is detrimental to structures because it
develops tensile stresses and leads to thermal cracking.
Prior knowledge of maximum temperature rise helps in averting such
hazards by taking suitable remedial measures such as pre cooling.
Computation of maximum temperature rise in mass concrete is a
tedious process and needs standard charts developed by USBR.
A computer program developed at CW&PRS quickly computes maximum
temperature rise in mass concrete once the thermal and strength properties
of the concrete mix are known. This
paper highlights the utility of the program. NBM& CW December 2003.
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Scour
at the base of flip-bucket spillways H. Md. Azmathullah, Prof. M. C. Deo, M.R.Bhajantri and P.B.Deolalikar Abstract Scouring in rocky bed downstream of spillway with flip-bucket is complicated due to the complex hydraulic and geological conditions. The estimation of various parameters determining the erosion resistance of the rock is difficult. The prediction of the local scour downstream of spillways can be made by means of oversimplified equations. These equations are sufficiently good for assessment of initial scour geometry to ensure the safety of dam as well as its abutments. Many researchers have developed empirical formulae considering various hydraulic as well as geological parameters. In the present study, extensive experimental results were collected and analyzed in order to investigate the effect of different parameters on scour downstream of a flip bucket spillway. It was found that the scour parameters are functions of downstream Froude number (discharge parameter), ratio of head to tail water depth, ratio of radius of slip bucket to tail water depth, ratio of sediment mean size to tail water depth and lip angle of the bucket. The functional relationships are expressed by dimensionless equations. Paper published in ISH Journal of Hydraulic Engineering, September,2004
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STUDIES
ON PERFORMANCE OF HORIZONTAL POWER INTAKES Y.N.
Srivastava, Senior
Research Officer, A.K.
Agrawal, Senior
Research Officer, S. L. Patil, Chief
Research Officer and P.B.
Deolalikar, Joint
Director Abstract Intakes structures are commonly used for withdrawing water from river, reservoir, and conveyance system of hydropower projects or for pumping stations. Formation of air-entraining vortices in front of intake is the result of complex interaction between many parameters and cause operational problems for turbine or pump and reduction of coefficient of discharge. Therefore, submergence provided at the intakes should be adequate to avoid air-entraining vortices. The submergence provided in horizontal intakes of Nathpa Jhakri, Chamera and Tala hydroelectric power projects were studied by way of hydraulic models at the Central Water and Power Research Station, Pune. The criteria for safe submergence without air-entrainment suggested by various researchers were compared with the actual submergence provided in all the three projects. Few guidelines provided in the literature were fitting well with the model results whereas other guidelines including one, which is suggested by IAHR manual, appeared to be highly conservative. The
paper published in “ISH Journal of Hydraulic Engineering
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CLOSURE
TO TECHNICAL NOTE ON “INTEGRATING EQUATION OF GRADUALLY VARIED FLOW” Ramappa G. Patil, Vasant N. Diwanji, and Rajnikant M. Khatsuria Abstract The
writers thank the discusser for their interest in the paper. The
“exponent method” maintains the rate process as described in the
differential equation and there is no need to divide the reach into
subreach to get the required accuracy. The method was obsolete because of
the accuracy limitations. This method addresses the accuracy limitation
and it can be used to solve many of the open channel flow problems
reliably and effectively. There are
many different expressions for “M” and “N”, which can be used in
the integration and one among them [Eq.(15)] is as suggested by the
discusser. The writers are of the view that the expressions as assumed by
Chow (1955) and improved by the writers are based on the proper theory.
The accuracy claimed in Table 2 by the discusser is due mainly to the
improved computational methods employed rather than the modified
expressions [Eqs. 15(a and b)] or the integration method. Jl. of Hydr. Engg.,ASCE
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S.N.Das
and S.K.Das The prediction of resonance is very important with respect to the vessels stability in the early stages of design. In this paper, an efficient modeling approach is presented to determine coupled roll and yaw motions of a symmetric and slender floating body when the influences of small amplitude regular waves are dominant. The angular motions described in time domain by considering all internal and external forces are transformed into frequency domain to obtain motion characteristics. We adopt a semi-analytical treatment to obtain roll and yaw motions and derive system instability due to roll resonance. To compute hydrodynamic forces, we employ strip theory method where frequency dependent sectional added-mass, damping and restoring coefficients are derived from the Frank’s close-fit curve. Numerical experiments carried out for a vessel of mass 19,190 ton under the action of wave of frequencies 0.56 and 0.76 rad/s with zero and non-zero initial conditions are reported and the effect of various parameters on system stability is investigated. Model results indicate that damping factor (ς) plays a pivotal role when wave encountering frequency (ω) and undamped natural frequency (β) are nearly equal. The essence of this study lies in the efficient modeling technique to evaluate damping factor and critical encountering frequency regime for a given ship particulars when experimentally derived resonance zone is absent. Applied Mathematical Modelling, Volume 29, Issue 1, January 2005, Pages 19-34
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DETERMINATION
OF COUPLED SWAY, ROLL, AND YAW MOTIONS OF A FLOATING BODY IN REGULAR WAVES S. N. DAS and S. K. DAS Abstract This paper investigates the motion response of a floating body in time domain under the influence of small amplitude regular waves. The governing equations of motion describing the balance of wave-exciting force with the inertial, damping, and restoring forces are transformed into frequency domain by applying Laplace transform technique. Assuming the floating body is initially at rest and the waves act perpendicular to the vessel of lateral symmetry, hydrodynamic coefficients were obtained in terms of integrated sectional added-mass, damping, and restoring coefficients, derived from Frank's close-fit curve. A numerical experiment on a vessel of 19190 ton displaced mass was carried out for three different wave frequencies, namely, 0.56 rad/s, 0.74 rad/s, and 1.24 rad/s. The damping parameters ( ςi) reveal the system stability criteria, derived from the quartic analysis, corresponding to the undamped frequencies ( βi). It is observed that the sway and yaw motions become maximum for frequency 0.56 rad/s, whereas roll motion is maximum for frequency 0.74 rad/s. All three motions show harmonic behavior and attain dynamic equilibrium for time t>100 seconds. The mathematical approach presented here will be useful to determine seaworthiness characteristics of any vessel when wave amplitudes are small and also to validate complex numerical models. IJMMS 2004:41 (2004)
2181-2197
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PRE
AND POST-EXCAVATION CROSS-HOLE SEISMIC AND GEOTOMOGRAPHIC STUDIES FOR A
NUCLEAR POWER PROJECT R.S.Wadhwa,
N.Ghosh, M.S. Chaudhari, Ch. Subba Rao and Raja Mukhopadhyay ABSTRACT The
foundation site response evaluation to earthquake forces requires
determination of both compressional and shear wave velocities. This
information allows less conservative safety margins and thereby helps in
reducing the cost of building construction. Cross-hole seismic
studies in NX size (~80 mm dia) boreholes to evaluate Compressional (P-)
and Shear (S-) wave velocities upto 51 m depth from the surface (EL
100 m) were carried out at Reactor Building (RB) RB-3 and RB-4
sites. It was found that at RB-3 site, the P-wave velocity was 5400 m/sec
while the shear wave velocity with depth ranged between 2900 m/sec and
3200 m/sec. The
RB-3 site was then excavated upto El 79.4 m and the rock was grouted by
cement slurry. To study the effect of removal of overburden and blasting
on the quality of rock, as also to decide the exact value of shear wave
velocity to be adopted for designing the foundation of reactor building,
cross-hole seismic studies upto EL 62.4 m were carried out. In addition to calculating the average wave velocities, the post-excavation cross-hole data were also analysed by seismic ray geotomography to evaluate velocity field distribution with depth. The pre and post excavation P- and S- wave velocity values were similar from which it was inferred that blast energy was contained and extension of fractures was not inferred. Also post P- and S-wave velocity tomograms revealed that the velocities in horizontal and vertical directions were same indicating that the distribution of stresses in both directions was of the same order and inhomogeneities have no preferential direction of orientation. The Journal of Indian Geophysical Union
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Real-Time
Operation of Reservoir system for irrigation scheduling H.Md.Azmathullah; Sandeep M Narulkar; M.R.Bhajantri; P. B. Deolalikar Synopsis There is an increasing awareness among the irrigation planners and engineers to plan and operate reservoir systems at maximum efficiency and to derive maximum benefits from them. As a result, considerable work has been done on reservoir operation for known total irrigation demand on the one hand and on optimal allocation of the available water at the farm level to crops on other. Very few studies have been conducted to derive optimal reservoir operation policies integrating the reservoir operation with the on-farm utilisation of water by the various crops. The present paper deals with the development of a model for real-time reservoir operation. The present study demonstrates the applicability of the model developed for a existing Chiller reservoir system in Madhya Pradesh. Proc.
Fifth International R & D Conference, February, 2005,
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Prediction
of Throw Distance and Maximum Scour Location H.Md.
Azmathullah, Research Assistant; V.V. Bhosekar,
Chief Research
Officer; M.R. Bhajantri, Senior
Research Officer
and P. B. Deolalikar, Joint Director Synopsis The spillway with flip bucket as energy dissipator satisfies both requirements of safety and economy. This paper reviews available literature on scour downstream of flip bucket and discusses jet trajectory estimation relationships. Many researchers have developed empirical formulae considering different hydraulic parameters and bucket configurations. An attempt has been made in this paper to estimate the location of maximum scour using parameters such as q, H1 R, d50, dw, and lip angle of the bucket. Extensive experimental results were collected and analyzed in order to investigate the effect of different parameters on throw distance and scour location downstream of a flip bucket spillway. It was found that the scour parameter is functions of fall Froude number, ratio of head to tail water depth, ratio of radius of flip bucket to head, ratio of sediment mean size to head and lip angle of the bucket. The functional relationship is expressed by dimensionless equation. The results of this study can be used to predict the location of maximum scour downstream of the flip bucket spillway. Proceeding
of Conference on Development of Hydropower Projects – A Prospective
Challenge
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HYDRODYNAMIC
SIMULATION OF FLOW OVER SPILLWAY USING WEAKLY COMPRESSIBLE FLOW
FORMULATION M.R. Bhajantri, T.I. Eldho and P.B. Deolalikar Abstract Acquiring necessary insight and understanding the complete hydrodynamics of flow features over spillway is very essential in the spillway design. Spillway hydrodynamics can be obtained through physical modelling or computer modelling. Physical modelling of spillway is expensive, cumbersome and time consuming. Numerical simulation of rapidly varied, supercritical, free surface turbulent flow over spillway with all flow regimes is a challenging task. This paper explains the formulation of numerical model based on weakly compressible flow formulation for flow over a spillway. The developed model is used to investigate the hydraulic characteristics of flow over spillway crest profile by simulating the velocity distribution, pressure distribution and discharge characteristics. The numerical model was further applied to a case study of the spillway with elliptic upstream profile and broad crested parabolic downstream crest profile. The observed values of pressures, water surface profile and discharge characteristics on the physical model have been used to compare with the values calculated from the numerical model. XXXI IAHR Congress, Seoul, September 11-16, 2005.
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Neural
Networks for Estimation of Scour Downstream of a Ski-Jump Bucket H.
Md. Azmathullah; M. C. Deo; and P. B. Deolalikar Abstract The estimation of scour downstream of a ski-jump bucket has remained inconclusive, despite analysis of numerous prototypes as well as hydraulic model studies in the past. It is partly due to the complexity of the phenomenon involved and partly because of limitations of the traditional analytical tool of statistical regression. This paper addresses the latter part and presents an alternative to the regression in the form of neural networks. The depth of the scour hole developed along with its width and length is predicted using neural network models. A network architecture complete with trained values of connection weight and bias and requiring input of grouped parameters pertaining to discharge head, tail water channel depth, bucket radius, lip angle, and median sediment size is recommended in order to predict the depth, the location of maximum scour, as well as the width of scour hole. The neural network predictions have been compared with traditional statistical schemes. Although the common and simple feed forward back propagation network took a very long time to train as compared to some advanced schemes, it was found to impart equally reliable training as the latter. Use of causative variables in grouped forms was found to be more rewarding than that of their raw forms probably due to lesser scaling effect. ASCE, Journal of Hydraulic Engineering, 131 (10), 898-908.
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HYDRAULIC
MODEL STUDIES FOR TALA DAM SPILLWAY, BHUTAN P.C. Pethe,Chief Research Officer; M.R. Kulkarni, Asstt. Research Officer; Mrs. V.V.Bhosekar, Chief Research Officer; P.B. Deolalikar, Joint Director ABSTRACT
The Tala H.E. project envisages construction of 91 m high concrete gravity dam across river Wangchu near Honka and underground power house near Tala having installed capacity of 1020 W. The spillway is in the form of a battery of low-level sluices in the central portion of the dam. The spillway has to perform dual function of flood disposal as well as flushing of sediment. This paper presents a case study of hydraulic model studies in evolving the efficient hydraulic design of spillway, energy dissipator, intake and plunge pool. The major modifications suggested were introduction of curvature in dam axis, increasing number of spans from 4 to 5, introduction of divide walls, shifting of overflow spillway from right to left and location of the plunge pool. Journal
of Hydraulic Engineering, Indian Society of Hydraulics.
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Uniform and Critical Flow Computations Ramappa
G. Patil; J. S. R. Murthy; and L. K. Ghosh Abstract The application of theory developed for direct integration of gradually varied flow equations to uniform and critical flow computation greatly reduces the computational effort. A small generalized subroutine is able to compute accurately the various parameters involved in the computation for all types of natural and constructed cross sections. Although the equations are implicit, in a majority of cases the number of iterations needed to achieve the required accuracy is less than 3. The method is even useful for computation by hand held calculators. Journal
of Irrigation and Drainage Engineering
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SEDIMENTATION
STUDIES FOR LOHARINAG PALA PROJECT V.
G. Bhave, Chief
Research Officer; Neena Isaac, Senior
Research Officer; and M. S.
Shitole, Joint
Director SYNOPSIS Reservoirs are constructed across rivers for variety of purposes like power generation, municipal and industrial use, irrigation, recreation, flood moderation, etc. The velocities in river upstream of reservoir are reduced due to storage of water. As a result, the sediment transport capacity is reduced and sediment is deposited on upstream side. A literature review of available methods for estimation of sedimentation profile is presented. The commonly adopted approach for estimation of such profile involves long-term simulation over 25-50 years. Such a criteria although suitable for reservoirs having storage capacity much larger than the average annual sediment inflow, cannot be used for reservoirs with smaller capacity. Such reservoirs are generally used for run-of-river power generation projects. A new criterion for termination of simulation is suggested. Case study for estimation of sedimented bed profile of reservoir across river Bhagirathi is presented. The results indicated maximum rise in bed of 3.87m. The likely loss of revenue due to shutdown required for flushing is estimated at full generation capacity. Proceeding
of Conference on Development of Hydropower Projects – A Prospective
Challenge
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PLANNING
OF A HYDRO PROJECT WITH DERISORY DATA V.
G. Bhave, Chief
Research Officer;
M. S. Shitole, Joint
Director SYNOPSIS Most of the developing nations are facing the problem of power shortages and accordingly planning of power projects gains high priority. The quantum of shortage would show a rising trend unless the rate of growth of generation is overriding the rate of growth of demand. Planning of a hydro project begins with site selection for storage or diversion structure, desilting chamber, water conductor system, surge tank, pressure release valve, power house, etc. The efficiency of water use would be high if maximum power generation is achieved with minimum water. Thus, estimation of water availability becomes an important step. These studies can be carried out easily, if adequate, consistent and long term discharge data are available. The authors have recently completed such studies and experienced that good data of adequate duration are not available. Different approaches under such situation are delineated and two ten-day flow series are derived for duration of 31 years and 20 years. A comparison of two series is carried out and the series to be used for estimation of power potential at the project site on a Himalayan river in Uttaranchal state is selected. Ten day flow volumes on 90 % and 50 % dependability are estimated. Proceeding
of Conference on Development of Hydropower Projects – A Prospective
Challenge
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