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A sound coding strategy for a cochlear implant translates the incoming sound signal into parameters for the electrical pulse pattern to be delivered by the implant, the pulse amplitudes and timings across electrodes. This basic sound coding is accompanied by noise reduction and de-reverberation techniques which clean the sound signal prior to pulse processing, together achieving good performance in many listening situations. Without the explicit noise reduction, the common envelope coding onto fixed, high-rate pulse trains leads to problems with sound localization and listening in situations with noise and reverberation. One reason is seen in the lack of spectral and temporal coding precision due to interaction between stimulation pulses at the electrode-nerve interface and due to using high pulse rates. For example, refractoriness and current-spread across channels make it hard to anticipate which electric pulses will evoke a neural response and thus to code temporal fine structure information. In recent years, several models for the auditory nerve response to sequential electrical pulsatile stimulation, such as the Sequential Biphasic Leaky Integrate-and-Fire (S-BLIF) model (Takanen and Seeber, code at doi: 10.5281/zenodo.4674563), have been developed, which consider non-linear interactions at the electrode-nerve interface due to refractoriness, adaptation, facilitation and accommodation. These models compute the probable neural response for a given electrical stimulation sequence, which for the S-BLIF model also includes spike timing. Here we report from the ongoing development of a novel approach for a cochlear implant stimulation strategy which deviates from classical deterministic sound coding by using a model to anticipate the nerve's non-linear response. First, the processing order is inverse, as the strategy does not start from the sound. Instead, the nerve's spiking response is the target for which a suitable stimulation sequence needs to be found. A nerve response model is placed in the loop of an optimization strategy which computes the pulse timings, amplitudes and durations needed to evoke a given nerve spike pattern. Different constraints can be implemented by penalizing the distance measure inherent to the optimization strategy, for example to prevent two pulses being placed at the same time on different electrodes or to trade a higher pulse amplitude against placing two or more short pulses to utilize facilitation effects. For example, classical fine structure coding approaches would code a tone into an electric pulse train of constant amplitude with a rate corresponding to the fundamental frequency. Instead, to obtain the anticipated regular spiking response of the nerve, an irregular stimulation sequence is needed which overcomes the refractoriness and other non-linear effects in the electrode-nerve interface. The article shows the recursive optimization on an example and discusses ideas how to overcome the convergence problems posed by non-monotonic changes in the distance measure due to the omission of spikes in absolute refractory states. In summary, by basing the cochlear implant strategy on an auditory nerve model and by taking the nerve's response as the target to be achieved, temporal information can be coded in a targeted way over the non-linear electrode-nerve interface., Funding:BMBF: 01 GQ 1004B

Overpressure systems are widely developed in the central depression and palco-uplift in the Yinggehai and Qiongdongnan basins. They can be divided into three types according to the origin of abnormally high formation pressure in the reservoirs, i.e. the autochthonous, vertically-transmitted and laterally-transmitted types. The autochthonous overpressure system results from rapid disequilibrium sediment loading and compaction. In the allochthonous overpressure system, the increase of fluid pressure in sandstone originates from the invasion of overpressured fluid flowing vertically or laterally through the conduit units. The autochthonous overpressure system occurs in the deep-lying strata of Neogene age in the central depression of the Yinggehai and Qiongdongnan basins. The vertically transmitted overpressure system is developed in the shallow strata of Late Miocene and Pliocene ages in the diapiric zone of the central Yinggehai basin, and the laterally transmitted overpressure system occurs in the Oligocene strata of paleo-uplifts, such as the structure of Ya-211 in the Qiongdongnan basin. The results indicate that the autochthonous overpressure system is generally a closed one, which is unfavorable for the migration and accumulation of hydrocarbons. In the allochthonous overpressure system, hydrocarbon accumulation depends on the relationship between the formation of overpressure systems and the spatial location and duration of hydrocarbon migration. The interval overlying the overpressure system is usually a favorable hydrocarbon accumulation zone if the duration of fluid expulsion coincides with that of hydrocarbon accumulation.

The stretching process of some Tertiary rift basins in eastern China is characterized by multiphase rifting. A multiple instantaneous uniform stretching model is proposed in this paper to simulate the formation of the basins as the rifting process cannot be accurately described by a simple (one episode) stretching model. The study shows that the multiphase stretching model, combined with the back-stripping technique, can be used to reconstruct the subsidence history and the stretching process of the lithosphere, and to evaluate the depth to the top of the asthenosphere and the deep thermal evolution of the basins. The calculated results obtained by applying the quantitative model to the episodic rifting process of the Tertiary Qiongdongnan and Yinggehai basins in the South China Sea are in agreement with geophysical data and geological observations. This provides a new method for quantitative evaluation of the geodynamic process of multiphase rifting occurring during the Tertiary in eastern China.

Taken as an example the Upper Permian reef section on the carbonate platform margin at Ziyun, Guizhou, the paper discusses the missing time of a hiatus surface, an important problem in chemical sequence stratigraphy, with the concept of cosmic chemistry. Then the paper proposes a series of new concepts for chemical sequence stratigraphy, including the condensation surface, relative compaction factor and time missing factor. Finally a quantitative curve of Late Permian relative sea–level change in the Ziyun area is presented with time coordinates.

Characteristics of deformation in the thrust belt and sequence stratigraphie framework in the foreland basin, structural features of the basin margin, and the episodic thrusting are studied in this paper by combining the eastern Qilian thrust belt and the Late Triassic foreland basin on the southwestern margin of Ordos. On this basis, a geological model and a mechanical model of coupling mechanism were established for the pair of thrust belt and foreland basin, and the subsidence and deposition process of the foreland basin were simulated on given parameters.

Reservoirs of the Karamay Formation occur as oil sandstones in outcrop in the Karamay oil field. Two types of high-quality reservoirs are present in this field: low-sinuosity channel sandstones and distributary-channel sandstones, each having different sediments, bounding surfaces, and architectural units. The low-sinuosity channel has coarse-grained sediments, a smaller scale, and relatively simple architectural units composed of intrachannel units and lithofacies that occur in a vertically stacked pattern. The distributary channel has fine-grained sediments, a larger scale, and relatively complex architectural units, which are reflected in the following three ways. (1) The distributary channels have three multiorder architectural units: an intrachannel unit, a macroform accretion unit, and a lithofacies unit. (2) Isolated barrier beds, whose permeability is lower, occur near third-order and fifth-order surfaces. (3) The evolution of the distributary channels has two stages. In the flooding stage, the sediments were coarse grained, and the intrachannel units were in a vertically stacked pattern. In the waning stage, the sediments were fine grained, and the intrachannel units were in a laterally stacked pattern. Reservoir heterogeneity of distributary-channel sandstones is revealed in the following three scales. (1) In a microscale range, the growth of pores is associated directly with lithofacies. The pore diameter and the throat width both increase with the coarsening of the grain size in the sediments. The anisotropic pore structure is reflected in the variation of permeability. The horizontal permeability parallel to the paleocurrent is the largest; the horizontal permeability perpendicular to the paleocurrent is intermediate; and the vertical permeability is the smallest. (2) At a channel scale, the fluid-flow units are demarcated according to the isolated barrier bed and porosity and permeability inside the distributary channel. The fluid-flow unit, distributed mainly in the middle–lower interval of the distributary channel or the intrachannel unit, is associated closely with third-order or fifth-order surfaces. The porosity and permeability inside the fluid-flow unit decrease gradually from its center to the margin and upper interval, depending on the spatial distribution of lithofacies. In this kind of lithofacies, which is characterized by a low matrix content and by coarse-grained sediments with large trough cross-beds, high porosity and permeability are commonly found. (3) In a lacustrine delta system, the distributary-channel sandstone has the best porosity and permeability and is the best reservoir.

An understanding to the chemistry of formation waters in sedimentary basins is important for many geological processes, such as the fluid-rock interaction, the migrating paths of fluid and the entrapment mechanisms of hydrocarbon. This paper deals with the salinity variation of formation water and diagenesis reaction in the abnormally pressured system. The Shiwu depression of the Songliao basin and the Yinggehai basin are selected for case studies. The studies indicate that there is a distinct difference in the chemistry of subsurface water between hydropressured and abnormally pressured systems. The Shiwu depression of the Songliao basin is composed of terrigeneous clastics in fluvial-lacustrine environments, which contain brackish water with salinity ranging from less than 1000 mg/L to 12000 mg/L. Water composition varies with depth and hydrochemical regions. In the underpressured strata deposited during the rifting period, the formation water is characterized by CaCl2 type water with high salinity. NaHCO3-dominanted water with lower salinity occurs at the hydropressured strata deposited during the post-rifting period. In this halite-free basin, brackish water may be attributed to the condensation of meteoric water and water-rock interaction. In the deeply buried underpressured water, a predominated diagenesis reaction resulting in enrichment of Ca and Cl and reduction of Na may be related to the albitization of plagioclase following the basinal fluid line (BFL). The Yinggehai basin constitutes clastic deposits in nearshore, neritic, shelf environments and contains brackish and saline water with salinity ranging from less than 15000 mg/L to 50000 mg/L. Pore water in these marine deposits must have originated from seawater. In the overpressured system, however, the formation water has much lower salinity and ion concentrations (except bicarbonate and carbonate) than normal seawater. The low salinity indicates that interstitial connate seawater is diluted by the water released from the transformation of smectite to illite. High bicarbonate and carbonate concentrations may contribute to mineral dehydration and kerogen-cracking reactions. Furthermore, low salinity water also occurs near and above the top of the geopressured zone in the diapiric structures, which may indicate that pore water with normal seawater salinity has been mixed by fresher saline water from deeper portions of the overpressured stratigraphic section.

The discovery of the WC13-1 and WC13-2 oil fields in the Zhu III subbasin of the Pearl River Mouth basin in the South China Sea has led to debate as to the oils on Horst Qionghai (HQH) are sourced from Half-graben Wenchang-A (HGWC-A) or Half-graben Wenchang-B (HGWC-B). Using the previous findings of sequence stratigraphers, this paper further analyzes the sedimentological characteristics of the Zhuhai and Zhujiang Formations and points out that the sandstones deposited on the unconformities (basement, T 6 and T 7 ) possess good porosity, permeability and lateral connectedness for hydrocarbon migration. The depositional systems and facies for the major reservoir rocks had gradually changed from fan-delta and semi-enclosed bay via barrier islands and washover to tidal flats, tidal channels and tide-influenced shoreface in response to the rise in sea level in the early Miocene. The sandy carrier beds of the transgressive systems tract in the Zhujiang Formation, especially in Zhujiang Formation II, act as the principal migration conduits for the WC13-1 and WC13-2 oil fields. Measurement of sandstones in drilling holes shows an increase in porosity in the Zhujiang Formation II and implies that the oil had ever passed through. Furthermore, the structural morphologies of T 5 and T 4 demonstrate that there are two salient structural noses connecting HQH with the HGWC-B and plunging into HGWC-B. T 5 , a regional muddy seal, seals the porous standstones underneath and accounts for the key role played by the sandy carrier beds in transporting the oils generated in HGWC-B to HQH. Correlation of oils in HQH and HGWC-B supports the plausibility of this migration pathway.

Intensely overpressured compartments are present in the centre of the Yinggehai Basin, South China Sea. In this part of the basin, a diapiric area can be distinguished from a non-diapiric area; structures in the former area result from shale diapirism at depth, and from the movement of hydrothermal fluids at more shallow levels. In the diapiric zone, the top of the overpressured compartment is relatively shallow (1,500m to 2,500m deep), whereas it is more than 3,200m deep in the non-diapiric area. The top of the overpressured compartment in the diapiric zone has been raised to relatively shallow levels due to vertical fluid expulsion. Hydrofracturing has occurred in the Neogene- Quaternary marine sedimentary succession, particularly in mud-rich intervals such as the Lower Member of the Pliocene Yinggehai Formation. Hydrofracturing may have allowed the rapid lateral and vertical migration of enormous volumes of pore fluids. The presence of additional steeply-dipping faults in the diapiric area may have led to vertical expulsion of fluids from overpressured compartments to normally-pressured areas, and caused the top of the overpressured compartment to be uplifted. Gaseous hydrocarbons are assumed to have migrated vertically through fractures around diapiric structures from overpressured to normally-pressured zones. We believe that this mechanism has had a significant effect on hydrocarbon transport and accumulation in the Yinggehai Basin.