Day 1 :
Keynote Forum
Dmitry A Kukushkin
Researchers in Geology, LLC, USA
Keynote: Lineament field distortion and its analysis
Time : 10:35-11:05
Biography:
Dmitry Kukushkin is the Cofounder of Researchers in Geology, LLC (FL, USA). He was was born in 1947 in Moscow, USSR (now Russia). He studied in Moscow Geological Prospecting Institute from 1965 to 1970. In 1971 he began working in the field of geological research and prospecting, mostly in Siberia and Africa. Dr. Kukushkin was awarded his Ph. D. in geology in 1986. He has extensive experience in mapping and prospecting for oil, gas, metals (including gold), including the use of aerial and satellite images. Dr. Kukushkin developed a new method for analyzing aerial and satellite images that allows locating sites with a high potential for the presence of oil, gas, and/or metals. His method also helps to reduce expenses for drilling and accelerate the development of sites.
Abstract:
Rectilinear details of landscape – lineaments – are the most numerous elements detectable on aerial and space photos of Earth's surface. Linea¬ments form a complex web on delineation maps of aerial and space photos. Photogeologists consider lineaments to be the traces of interaction of fractures or faults of Earth’s crust with the surface, having direct and indirect relationships with geological structures. Lineament field is the surface manifestation of fields of tension, stress and deformation of rocks. General lineament field is the result of superimposition of multiple lineament fields of various scales, such as planetary, regional, and local. The causes of planetary fields of tensions, brittle disloca¬tions and lineament fields are rotational and tide tensions in the Earth's crust. Within regional geological structures regional fields of stress and tensions dominate, creating regional field of brittle dislocations and regional lineament field, which is one of the manifestations of regional stresses and tensions. Local geological structures, containing mineral deposits, are characterized by fields of stress and tension, brittle dislocations, and lineaments, superimposition and interaction of lineament fields of different types and scales in Earth’s crust and in time for general lineament field where its com¬ponents affect and distort each other. Therefore traditional methods, such as the lineaments density analysis and rose-diagrams drawing are unsuccessful in geological practice. Using physical modeling and mathematical filtration, we have developed a method that allows separation of lineament fields of different scales and nature. This method has been successfully tested on different scales in Siberia and Africa on the total area of more than 650000 km2 (250000 sq. miles).
Keynote Forum
Bill X Hu
Florida State University, USA
Keynote: Numerical study on groundwater flow cycling in the Woodville Karst Plain controlled by seawater intrusion to a Karst aquifer through a conduit network using CFPv2
Time : 10:00-10:35
Biography:
Bill X Hu is the Professor of the department of Earth, Ocean & Atmospheric Science at Florida State University. He is also the Adjunct Faculty Member of the Department of Geosciences at Nanjing University He has done his Ph.D. from Purdue University in the year of 1996. He has more than 45 publications in many Journals.
Abstract:
Groundwater flow cycling in the Spring Creek spingshed and interaction between groundwater and seawater in the spring sub ground conduit is numerically simulated using the CFPv2, the latest research version of MODFLOW-CFP (Conduit Flow Process). Spring Creek Springs and Wakulla Spring located in a marine estuary and 11 miles inland respectively are two major groundwater discharge spots in theWoodville Karst Plain (WKP), North Florida, USA. A conceptual model for three repeating phases of groundwater flow cycle between the two springs and recharge from a major surface creek (Lost Creek) was proposed from a low rainfall period to a heavy rainfall period then back to a low rainfall period. Tracer tests and cave diving found a complex sub ground Karst conduit network connect the two springs. The flow rate, salinity and sea level at the Spring Creek Springs could significantly affect freshwater discharge and water stage at Wakulla Spring simultaneously. Based on the conceptual model, the groundwater flow model is developed using CFPv2 and calibrated by field measurements. Non-laminar flow, direct recharges in conduits, time-variable water stage at the submarine spring and flow exchange between conduits and porous medium are implemented in the numerical model. The developed numerical model is used to simulate the seawater intrusionand fresh groundwater contamination through the submarine spring’s conduit and its influence onthe inland spring discharge from June 2007 to June 2010. Simulated results of two spring’s discharges match reasonably well with measurements and quantitatively present the three-phase groundwater flow cycling. The regional flow field and relationship between inland spring and submarine spring are studied and evaluated as well in a prediction of sea level rise.
- Track 1: Geology and Mineral Resources Track 2: Geophysics and Geochemistry Track 3: Environmental Geology Track 9: Exploration Geology Track 10: Paleontology and Paleobiology Track 5: Petroleum Geology
Session Introduction
Dmitry A Kukushkin
Researchers in Geology, LLC, USA
Title: Lineament field distortion and its analysis
Time : 10:35-11:05
Biography:
Dmitry Kukushkin is the Cofounder of Researchers in Geology, LLC (FL, USA). He was was born in 1947 in Moscow, USSR (now Russia). He studied in Moscow Geological Prospecting Institute from 1965 to 1970. In 1971 he began working in the field of geological research and prospecting, mostly in Siberia and Africa. Dr. Kukushkin was awarded his Ph. D. in geology in 1986. He has extensive experience in mapping and prospecting for oil, gas, metals (including gold), including the use of aerial and satellite images. Dr. Kukushkin developed a new method for analyzing aerial and satellite images that allows locating sites with a high potential for the presence of oil, gas, and/or metals. His method also helps to reduce expenses for drilling and accelerate the development of sites.
Abstract:
Rectilinear details of landscape – lineaments – are the most numerous elements detectable on aerial and space photos of Earth's surface. Linea¬ments form a complex web on delineation maps of aerial and space photos. Photogeologists consider lineaments to be the traces of interaction of fractures or faults of Earth’s crust with the surface, having direct and indirect relationships with geological structures. Lineament field is the surface manifestation of fields of tension, stress and deformation of rocks. General lineament field is the result of superimposition of multiple lineament fields of various scales, such as planetary, regional, and local. The causes of planetary fields of tensions, brittle disloca¬tions and lineament fields are rotational and tide tensions in the Earth's crust. Within regional geolo¬gical structures regional fields of stress and tensions dominate, creating regional field of brittle dislocations and regional lineament field, which is one of the manifestations of regional stresses and tensions. Local geological structures, containing mineral deposits, are characterized by fields of stress and tension, brittle dislocations, and lineaments, superimposition and interaction of lineament fields of different types and scales in Earth’s crust and in time for general lineament field where its com¬ponents affect and distort each other. Therefore traditional methods, such as the lineaments density analysis and rose-diagrams drawing are unsuccessful in geological practice. Using physical modeling and mathematical filtration, we have developed a method that allows separation of lineament fields of different scales and nature. This method has been successfully tested on different scales in Siberia and Africa on the total area of more than 650000 km2 (250000 sq. miles).
Bill X Hu
Florida State University, USA
Title: Numerical study on groundwater flow cycling in the Woodville Karst Plain controlled by seawater intrusion to a Karst aquifer through a conduit network using CFPv2
Time : 10:05-10:35
Biography:
Bill X Hu is the Professor of the department of Earth, Ocean & Atmospheric Science at Florida State University. He is also the Adjunct Faculty Member of the Department of Geosciences at Nanjing University He has done his Ph.D. from Purdue University in the year of 1996. He has more than 45 publications in many Journals.
Abstract:
Groundwater flow cycling in the Spring Creek spingshed and interaction between groundwater and seawater in the spring sub ground conduit is numerically simulated using the CFPv2, the latest research version of MODFLOW-CFP (Conduit Flow Process). Spring Creek Springs and Wakulla Spring located in a marine estuary and 11 miles inland respectively are two major groundwater discharge spots in theWoodville Karst Plain (WKP), North Florida, USA. A conceptual model for three repeating phases of groundwater flow cycle between the two springs and recharge from a major surface creek (Lost Creek) was proposed from a low rainfall period to a heavy rainfall period then back to a low rainfall period. Tracer tests and cave diving found a complex sub ground Karst conduit network connect the two springs. The flow rate, salinity and sea level at the Spring Creek Springs could significantly affect freshwater discharge and water stage at Wakulla Spring simultaneously. Based on the conceptual model, the groundwater flow model is developed using CFPv2 and calibrated by field measurements. Non-laminar flow, direct recharges in conduits, time-variable water stage at the submarine spring and flow exchange between conduits and porous medium are implemented in the numerical model. The developed numerical model is used to simulate the seawater intrusionand fresh groundwater contamination through the submarine spring’s conduit and its influence onthe inland spring discharge from June 2007 to June 2010. Simulated results of two spring’s discharges match reasonably well with measurements and quantitatively present the three-phase groundwater flow cycling. The regional flow field and relationship between inland spring and submarine spring are studied and evaluated as well in a prediction of sea level rise.
Mohamed Ibrahim Dosouky Helal
Cairo University, Egypt
Title: Immobilization of Cd and Pb in polluted soils using nano particles
Time : 11:25-12:05
Biography:
Mohamed Ibrahim Dosouky Helal is the Professor of Soil Chemistry at Cairo University Egypt. He has done his Ph.D. in Soil Science from Cairo University in 1988. He is also the Vice President of National Committee of Soil Sciences. He published 8 articles in international journals as recorded by Scopus data base. He has 1- Membership in Egyptian Soil Science Society since 1984 and with African Soil Science Society since 1988.
Abstract:
Nanotechnology offers a number of highly efficient and less costly techniques that could work to immobilize contaminants. Nano-particles; nano scale zero valent iron “nZVI”, nZVI-bentonite, nanoalginite, and nano carbon; are used as a potential sorbents to immobilize Cd and Pb in polluted soils. These nano-particles are prepared in lab either using top-down or bottom-up methods, then characterized using transmission electron microscope (TEM). The prepared nano-particles proved to have very small size (less than 70 nm), high surface area (194.2-259.7 m2/g) and cation exchange capacity (42.5-47.7Cmolc/kg). Also, the prepared nano-particles proved high adsorption capacity for Pb and Cd, and high retention for the adsorbate metal. The maximum adsorption capacity of nano-particles ranged from 37450-93450 and 17850-25970 mg kg-1 for Pb and Cd, respectively. Moreover, except for nano carbon, only small quantities represent 10.8-33.4% and 13.7-35.6% of the previously adsorbed Cd and Pb, respectively, were released.
Ahmad Helman Hamdani
University of Padjadjaran, Indonesia
Title: Recent advancements in X-ray CT tomography as a geosciences tool for coalbed methane exploration
Time : 12:05-12:30
Biography:
Ahmad Helman Hamdani received his PhD in Geology with the topic of CBM from University Padjadjaran in 2013. He has experience of 20 years in coal and coalbed methane exploration Indonesia. He has also published his research in reputed journals.
Abstract:
The quantification of the volume and spatial disposition of pores, fractures or cleats and minerals in coals is a primary and fundamental requirement for CBM reservoir evaluation. Coal as a CBM reservoir is a complex polymeric material with complex porous structures which are important for flow pathway that determine the permeability and producibility of coalbed methane. The CT scan computed tomography is a non-destructive technique that can provide quantitative detection and visualization of interior structure of rocks in 3D within opaque objects. This paper will inform several applications illustrate the possibilities, specific advantages and limitations of CT for non-destructive coal characterization in describing the fracture and cleat characteristics including fracture-size patterns, network geometries in coal which is very useful in quantified and 3D visualization of the spatial disposition of minerals, pores and fractures in coals. As with every technique there are always some restrictions that can happen, however the CT scan technique proved to be an emerging non-destructive analysis which gives promising results in CBM exploration activities
Mutwakil Nafi
Dongola University, Sudan
Title: The descendants Clarkina of the Eurasian stock (Changhsingian) and the forms of Clarkina wangi at Ganxi, Xiakou and Tianqiao sections, South China
Time : 12:30-12:55
Biography:
Mutwakil Nafi has completed his Msc from University of Khartoum, Sudan and PhD (Petroleum geology- diagenesis) from China University of Geosciences and postdoctoral (Micropaleontology-conodont) studies from China University of Geosciences. He is associate professor at Dongola University, Faculty of Earth Sciences and Mining, Department of petroleum Geology, Sudan. He has published more than 20 papers in reputed journals and has been serving as an editorial board member of European Journal of Scientific Research. He is a Member of SCS (Subcommission on Carboniferous Stratigraphy) and SPS (Subcommission on Permian Stratigraphy).
Abstract:
The descendants Clarkina of the Eurasian stock (Changhsingian) are composed of C. changxingensis, C. changxingensis yini, C. deflecta, C. guangyuanensis, C. inflecta, C. iranica, C. liangshanensis, Clarkina longicuspidata, C. meishanensis meishanensis, C. meishanensis, C. orientalis, C. parasubcarinata, C. postwangi, C. prechangxingensis and C. predeflecta, C. preiranica sp. nov., C. subcarinata (Sweet), and C. wangi. One new species of C. preiranica sp. nov. has been recognized. Clarkina preiranica sp. nov. is very important because it is found at the same level with C. wangi. The base of the Changhsingian can be defined within an evolutionary lineage from C. longicuspidata to C. wangi based on a refined taxonomic approach. There are three forms of Clarkina wangi: (1) Those forms characterized by drop-like, with a short and wide platform, usually no free blade, fused carina looks like a high wall and reaching beyond the posterior margin., (2) Those forms characterized by a free blade, platform lenticular in outline, fused carina looks like a high wall and reaching beyond the posterior margin., (3) Those forms with high and highly fused posterior carina, which does not reach beyond the posterior margin. The base of the Changhsingian has been suggested as the first appearance datum (FAD) of Clarkina wangi which characterized by drop-like, with a short and wide platform, usually no free blade; fused carina looks like a high wall and reaching beyond the posterior margin.
Joseph Kokonyangi
Environmental and Natural Resources Commission, D R Congo
Title: The kibaran tin and columbite-tantalite province in eastern D.R. Congo: Structural control, Cassiterite shrimp vs K-Ar geochronology and implications to rodinia and gondwana tectonic
Time : 13:55-14:20
Biography:
Joseph Kokonyangi has completed his Ph.D. studies in 2005 at the Osaka City University in Japan and his Postdoctoral researches at Yokohama National University in Japan. From 2007 to 2010, he has worked as Professor and Director of the Tokyo Chapter of the Gondwana Institute for Geology and Geochronology. In 2011, he was elected as the member of lower house of the parliament of the democratic republic of congo in central Africa.
Abstract:
The Mesoproterozoic Kibaran Orogenic System of central Africa developed between 1.4 and 0.95 Ga (from rifting to post collisional stage). It hosts one of the world’s largest and valuable quartz and pegmatite veins mined for cassiterite, tungsten, columbite-tantalite, monazite, ilmenite, gold and REE since the 19s. The origin and time of emplacement of the mineralization is poorly constrained partly because, attempts to date the mineralization through their host rock andor associated silicates accessory minerals such as micas and feldspar have been hampered by uncertainties and disturbances of isotopic systems. An alternative approach is to date the ore themselves directly. In this paper, Pb-Pb SHRIMP geochronology was directly applied for the first time on the cassiterite occurring within quartz and pegmatite veins and those disseminated in associated peraluminous, two micas granitoids in the Kalima and Mitwaba areas of eastern Congo. K-Ar ages obtained on muscovite occurring together with the dated cassiterite in greisen are matched to the Pb/Pb SHRIMP data and the significances of individual dates are interpreted in the frame of the metallogeny of central Africa. Finally, the implication of these geochronological data to the understanding the blocking temperature of cassiterite is assessed. Geochronological data coupled with structural observationsare finally used to discuss the Rodinia and Gondwana tectonics between 1000 and 550 Ma in central Africa.
Olumuyiwa Michael Ajibade
Olabisi Onabanjo University, Nigeria
Title: Sediments toxicity in the rivers draining Ibadan metropolis, southwestern Nigeria
Time : 14:20-14:45
Biography:
Olumuyiwa Michael Ajibade is a faculty of the Department of Earth Sciences at Olabisi Onabanjo University, Nigeria.
Abstract:
The drainage structures in Ibadan Metropolis are depocenter for both industrial and domestic wastes/effluents influenced by cultural practices and landuse activities. These acts of man are often major contributors of potentially harmful elements (PHE) not only into the stream sediments but also the environment. These elements have their attendant health implications on man and the entire ecosystem as a whole. This study therefore examine the trace metal content in the sediments and evaluate their origin, pollution status and the bioavailability of these trace metals in the environment. Two hundred and thirty three (233) samples systematically collected from Agricultural, Industrial; old city and new city zones (zone 1, 2, 3, 4) respectively. These were analyzed using XRD and inductively coupled plasma-mass spectrometry (ICP-MS) and sequential leaches in the sediments as absorbed ions on clay, organic compounds, amorphous Mn and Fe, sulphide and residue after digestion. XRD data revealed the dominant minerals as kaolinite, illite, montmorillonite and quartz. Potentially harmful metals concentrations range from Cu (18.30-513.00), Pb (40.30-5140.00), Zn (80.90-2450.00), As (0.20-7.10), Cd (0.08-24.40), Cu-Pb-Zn-Cd revealed highest concentrations in the old city (densely populated) and industrial areas of the city respectively. Geochemical maps revealed the densely populated zones as hotspots for the PHE’s. Pollution Load Index (PLI) values for zones 1 to 4 include PLI-127, 471, 582, 512 respectivelyindicating polluted sediments and metal sourceslink tohuman and landuse activities. Percentages of Pb, Zn and Cd ranged correspondingly from 26.4-43.5; 25.5-36.9 and 17.0-51.0 in the exchangeable fraction indicating their bioavailability to the environment. Cu, Pb, Zn, Cd and Ni concentrations in all the zones exceeded the threshold values in the sediment quality guidelines (SQGs) suggesting that the sediments were polluted. Metals concentration and degree of contamination has been linked to high population density, urbanization and increased human activities in the river channels.
Laniyan Temitope A
Olabisi Onabanjo University, Nigeria
Title: Impact of urban activities on ground water qualities in Abeokuta southwestern, Nigeria
Time : 14:45-15:10
Biography:
Laniyan T A is a Lecturer in the Department of Earth Sciences, Olabisi Onabanjo University, Ago – Iwoye, Ogun State Nigeria. Her Area of Specialisation: Applied Geochemistry.
Abstract:
Pollution of ground water has become a major environmental problem. Anthropogenic impacts on groundwater within different zones of Abeokuta, Southern Nigeria were evaluated. The study area was divided into four zones; Crowded, Market, Residential and Industrial areas and it also involved the measurement of pH, electrical conductivity (EC) and total dissolved solids (TDS). Ground water samples were randomly collected and acidified with two drops of concentrated nitric acid and determined for elemental constituent using ICP-MS. Then of Physicochemical parameters were in the range 67-649 ppm for TDS; 6.6-8.9 for pH and 103.07-984.61 (µScm-1) for EC respectively. Elemental analysis revealed mean concentrations in decreasing order of Na>Ca>K>Mg>Fe>Mn>Zn>Pb>Cd>As>Cu for cations and Cl- > SO42-> NO3- for anions. Cations occurred within WHO permissible limits for groundwater except K, Pb and Ca while Cl- and NO3- were above the limit for anions. The high values of Cl- and NO3- were from the influence of tie and dye in the study area. The contamination factor (C.F) and geo-accumulation Index (Igeo) revealed no contamination in the cations except for Cd and Pb due to the effect of fuel combustion and quarry found behind the residential area. Conclusively, ground water from industrial and crowded zones of the study area was more contaminated than the residential zone.
Yang Tian
China University of Petroleum, China
Title: Coupling of dynamics and physical property in hydrocarbon accumulation period control the oil-bearing property of low permeability reservoir: Take the case of the low permeability turbidite reservoir of the middle part of the third member of Shahejie formation in Dongying Sag
Time : 15:55-16:15
Biography:
Tian Yang has completed his B.E and M.E. in Geology from School of Geosciences, China University of Petroleum, China. He will complete his Ph.D. in July 2016 from School of Geosciences, China University of Petroleum (CUP).
Abstract:
The coupling relationship between physical property and dynamics of hydrocarbon accumulation period determines oil bearing property of low permeability reservoir. Studies on reservoir physical property evolution and accumulation dynamics of low permeability turbidite reservoirs have been carried out by means of core observation, thin section identification, fluid inclusion analysis, carbon and oxygen isotope analysis, mercury penetration, physical property testing, basin modeling, combined with analyses of burial history, thermal history and hydrocarbon charge history in the middle part of the third member of the Shahejie Formation in Dongying Sag. The petrophysical cutoffs of reservoirs in the accumulation period were calculated after recovery of accumulation dynamics and reservoir pore structures and then the distribution laws of the oil-bearing property of reservoirs controlled by the matching relationship between dynamics and physical property during accumulation period were summarized. On the basis of diagenesis features study and with the guide of ‘diagenesis-filling’ evolution sequence, the reservoirs can be subdivided into four kinds of diagenetic facies. The reservoir experienced two period of hydrocarbon accumulation. In the early accumulation period, reservoirs have middle to high permeability from 10×10-3 μm2 to 4207.3×10-3 μm2 except diagenetic facies (A). In the later accumulation period, reservoirs have low permeability from 0.015×10-3 μm2 to 62×10-3 μm2 except diagenetic facies (C). The fluid pressure generated by hydrocarbon forming is 1.4 Mpa to 11.3 Mpa with an average of 5.14 Mpa and the surplus pressure is 1.8 Mpa to 12.6 Mpa with an average of 6.3 Mpa in the early accumulation period. In the later accumulation period, the fluid pressure generated by hydrocarbon forming is 0.7 Mpa to 12.7 Mpa with an average of 5.36 Mpa and the surplus pressure is 1.3 Mpa to 16.2 Mpa with an average of 6.55 Mpa Different kinds of reservoirs all can accumulate oil in the early accumulation period. Different kinds of reservoirs all can accumulate oil under high accumulation dynamics whereas reservoir with diagenetic facies (A) and diagenetic facies (B) could not accumulate oil in the late accumulation period. Vertically, when burial depth of turbidite reservoir is more than 3000 m, reservoirs are all oil-filled and the hydrocarbon-filling degree is higher and so can the isolated lenticular sand bodies. When burial depth of turbidite reservoir is less than 3000 m, the development of oil-source faults controlled the accumulation of reservoirs and the isolated lenticular sand bodies cannot get hydrocarbon filling. For flat surface, hydrocarbon always accumulated in reservoirs around the oil-source faults and areas near the center of subsag with high accumulation dynamics.
Guanghui Yuan
China University of Petroleum, China
Title: Feldspar dissolution, authigenic clays and quartz cements in open and closed sandstone geochemical systems during diagenesis: Typical examples from two sags in Bohai Bay Basin, east China
Time : 16:15-16:35
Biography:
Guanghui Yuan has completed his Bachelor degree in Geology at the age of 23 from China University of Petroleum. He will complete his PhD in June 2015 from China University of Petroleum. He has published more than 15 papers in reputed journals.
Abstract:
Feldspar dissolution and precipitation of clays and quartz cements are important diagenetic reactions in sandstone reservoirs and can have great significance in reservoir quality evolution. We examined two sets of burial sandstone reservoirs to determine if the diagenetic systems were open or closed and investigated the mass transfer of products from leached feldspars and its impact on reservoir quality. One of the reservoirs is the Eocene sandstone buried 2.5-4.0 km below sea level (BSL) in the Nanpu Sag and the other is the Eocene sandstone buried 1.5-4.5 km BSL in the Dongying Sag. Both sandstones consist mainly of lithic arkoses and feldspathic litharenites, and have feldspar secondary pores. Widely developed fractures in the Paleogene and Neogene strata, low salinity and negative hydrogen isotopic composition of pore waters indicate massive meteoric water flux in sandstones of the Nanpu Sag. In the sandstones, extensive leached feldspars are generally accompanied by small amounts of authigenic clays and quartz. Authigenic clay in sandstones is mainly kaolin with little illite even at high temperature (>125° C). The low abundance of authigenic clays and quartz and low water salinity indicate that much of the K+, Al3+ and SiO2 (aq) released from feldspar dissolution were exported from the sandstone system. Therefore, extensive feldspar dissolution enhanced much porosity and permeability. In contrast, limited fractures and high water salinity indicate little meteoric water flux in sandstones of the Dongying Sag. Sandstones containing extensive feldspar dissolution were accompanied by massive quantities of authigenic clays and quartz. Kaolin dominates in sandstones at shallower depth (<3.1 km BSL) while illite dominates at greater depth (>3.1 km BSL) where temperature exceeds 125° C. The presence of abundant clays and quartz indicates that Al3+ and SiO2 (aq) released from leached feldspars were retained in the sandstone system. The dominance of authigenic illite at greater depth indicates sufficient K+ were retained within the connate water for illitization of kaolin and feldspar to occur. Feldspar secondary porosity in thin sections can be up to 3% but little porosity (<0.25%) is enhanced. Primary macropores are lost as clays and quartz precipitate while the proportion of microporosity increases occurring between clay crystals and within the partially dissolved remains of feldspars. The overall result is that permeability is significantly degraded.