Oblique Penetrations Research Articles

Igneous intrusion contact metamorphic system and its reservoir characteristics: A case study of Paleogene Shahejie Formation in Nanpu sag of Bohai Bay Basin, China

Taking the Paleogene Shahejie Formation in Nanpu sag of Bohai Bay Basin as an example, this study comprehensively utilizes seismic, mud logging, well logging, physical property analysis and core thin section data to investigate the metamorphic reservoir formed by contact metamorphism after igneous rock intrusion. (1) A geological model of the igneous intrusion contact metamorphic system is proposed, which can be divided into five structural layers vertically: the intrusion, upper metamorphic aureole, lower metamorphic aureole, normal sedimentary layers on the roof and floor. (2) The intrusion is characterized by xenoliths indicating intrusive facies at the top, regular changes in rock texture and mineral crystallization from the center to the edge on a microscopic scale, and low-angle oblique penetrations of the intrusion through sedimentary strata on a macroscopic scale. The metamorphic aureole has characteristics such as sedimentary rocks as the host rock, typical palimpsest textures developed, various low-temperature thermal metamorphic minerals developed, and medium-low grade thermal metamorphic rocks as the lithology. (3) The reservoir in contact metamorphic aureole has two types of reservoir spaces: matrix pores and fractures. The matrix pores are secondary “intergranular pores” distributed around metamorphic minerals after thermal metamorphic transformation in metasandstones. The fractures are mainly structural fractures and intrusive compressive fractures in metamudstones. The reservoirs generally have three spatial distribution characteristics: layered, porphyritic and hydrocarbon impregnation along fracture. (4) The distribution of reservoirs in the metamorphic aureole is mainly controlled by the intensity of thermal baking. Furthermore, the distribution of favorable reservoirs is controlled by the coupling of favorable lithofacies and thermal contact metamorphism, intrusive compression and hydrothermal dissolution. The proposal and application of the geological model of the intrusion contact metamorphic system are expected to promote the discovery of exploration targets of contact metamorphic rock in Nanpu sag, and provide a reference for the study and exploration of deep contact metamorphic rock reservoirs in the Bohai Bay Basin.

Trajectory characteristics of oblique penetration of projectile into concrete targets considering cratering effect

To better understand the trajectory characteristics of oblique penetration of projectile into concrete targets, the trajectory model of projectile based on the 2-D motion equations was established. The wake-separation effect and the cratering effect are both considered in this model. The model describing the cratering effect was established according to the splashing phenomenon of crushing medium at cratering stage. Furthermore, the reliability of the trajectory model was verified through a series of oblique penetrations experiments, and the predicted results agree well with the experimental data. Finally, influences of length-diameter ratio, caliber-radius-head, and the relative location of the center of mass on the trajectory characteristics were discussed. The results show that the asymmetric cratering effect is the main factor of trajectory deflection. The smaller the length-diameter ratio and caliber-radius-head, and the larger the relative location of the center of mass, the more obvious the trajectory deflection phenomenon. Compared with the caliber-radius-head, the length-diameter ratio and the relative location of the center of mass are the main factors affecting the stability of trajectory. In addition, the trajectory converges from a curvilinear motion to a linear motion. The characteristic convergence velocity depends linearly on the relative location of the center of mass and the impact velocity. Compared with the caliber-radius-head, length-diameter ratio and relative location of the center of mass, the impact velocity is the main factor affecting the characteristic convergence velocity.

Investigating the effect of preformed particle gel on conformance control of naturally fractured tight sandstone reservoirs: An experimental study using pressure transfer test method

The recovery of oil and gas resources is limited by the high water production from wells in unconventional reservoirs. While water intrusion prevention measures have been extensively investigated in highly permeable reservoirs, there has been limited research in tight unconventional reservoirs. In this study, a Pressure Transfer Test (PTT) method was used to evaluate the effect of preformed particle gel (PPG) on the conformance control of naturally fractured tight sandstone reservoirs. The study analyzed and compared four types of naturally fractured cores, and performed experiments on the PPG plugging effect under different natural fracture types, injection pressures, and salinities using a PTT device. The results showed that among the four fracture types, vertical and oblique penetrations had the highest plugging effect, with a 12% higher rate than fractures without effective channels. The injection pressure also had a significant impact on the plugging efficiency, with a 99.13% blocking rate at 12.5 MPa, which was almost completely plugged. Meanwhile, the salinity of the injected fluid had a decreasing effect on the PPG plugging efficiency, with the lower salinity of 1 wt% improving the plugging efficiency by 15% compared to high salinity. The experimental results and analysis were used to propose the plugging mechanism of PPG in different types of naturally fractured tight reservoirs. This study provides valuable experimental and theoretical references for the field application and further studies of PPG in naturally fractured tight reservoirs.

Three-dimensional trajectory prediction and analysis of elliptical projectile

This article establishes a three-dimensional trajectory model for an elliptical projectile into semi-infinite target based on rigid dynamics and the idea of isolation between the projectile and target. The reliability of the proposed model is verified through a series of normal and oblique penetrations, and the predicted results agree well with the experimental and simulation data. In addition, the effects of the structural parameters and striking conditions of the elliptical projectile on the trajectory stability are discussed. Compared with a circular projectile with a particular initial pitch or yaw angle, the anti-deflection ability of the elliptical projectile on its minor-axis side is increased, whereas that on the major-axis side is decreased. The introduction of a roll angle for the elliptical projectile results in two lateral resistances, causing a rotational motion along its longitudinal axis. Compared with a circular projectile with a particular initial attack or sideslip angle, an elliptical projectile exhibit increased anti-deflection ability on its major-axis side, and reduced anti-deflection ability on its minor-axis side. This preliminary study on the ballistic behavior of non-circular projectiles provides guidance for the design and application of such projectiles.

Fast algorithm for simulation of normal and oblique penetration into limestone targets

A fast algorithm is proposed to predict penetration trajectory in simulation of normal and oblique penetration of a rigid steel projectile into a limestone target. The algorithm is designed based on the idea of isolation between the projectile and the target. Corresponding factors of influence are considered, including analytical load model, cratering effect, free surface effect, and separation-reattachment phenomenon. Besides, a method of cavity ring is used to study the process of cavity expansion. Further, description of the projectile’s three-dimensional gesture is presented. As a result, the algorithm is coded for fast calculation, named PENE3D. A series of cases with selected normal and oblique penetrations are simulated by the algorithm. The predictions agree with the results of tests, showing that the proposed algorithm is fast and effective in simulation of the penetration process and prediction of the penetration trajectory.

Functional organization of speed tuned neurons in visual area MT.

We analyzed the functional organization of speed tuned neurons in extrastriate visual area MT. We sought to determine whether neurons tuned for particular speeds are clustered spatially and whether such spatial clusters are elongated normal to the cortical surface so as to form speed columns. Our data showed that MT neurons are indeed clustered according to preferred speed. Multiunit recordings were speed tuned, and the speed tuning of these signals was well correlated with the speed tuning of single neurons recorded simultaneously. To determine whether speed columns exist in MT, we compared the rates at which preferred speed changed in electrode tracks that traversed MT obliquely and normally to the cortical surface. If speed columns exist, the preferred speed should change at a faster rate during oblique electrode tracks. We found, however, that preferred speed changed at similar rates for either type of penetration. In the same data set, the rate of change of preferred direction and preferred disparity differed substantially in normal and oblique penetrations as expected from the known columnar organization of MT. Thus our results suggest that a columnar organization for speed tuned neurons does not exist in MT.

The organization and post-natal development of area 18 of the cat's visual cortex.

1. We made extracellular recordings from 1176 single units in area 18 of adult cats and kittens aged between 7 days and 10 weeks, and from 137 single units in area 17 in kittens aged between 12 days and 10 weeks. 2. All cells examined in area 18 of adult cats were visually responsive, 84% being orientation selective, 9% orientation biased and 7% non-oriented. Orientation columns and ocular dominance columns were identified. There was an over-all bias towards horizontal and vertical in the distribution of preferred orientations in the rostral part of area 18, where we were recording. 3. In area 18 of 7-day-old, visually inexperienced kittens the majority of cells (60%) were visually unresponsive; the remainder were either non-oriented (25%) or orientation biased (15%), and no orientation-selective units were found. Nevertheless there seemed to be a rudimentary columnar system, even in the youngest animals, in that orientation-biased cells tended to occur in clusters with neighboring neurones having similar orientation preferences. In normal animals of 3 weeks and younger we found that the distribution of preferred orientations of a sample of neurones in area 18 with receptive fields scattered over much of the left lower quadrant of the visual hemifield was biased to oblique orientations. 4. As in adult cats, most cells in area 18 in young kittens were binocularly driven, and periodic alternation of dominance along oblique penetrations, characteristic of ocular dominance columns, was sometimes seen, even at the earliest ages. 5. Many of the developmental changes that we observed in area 18 occurred during the first 4 post-natal weeks. Orientation selectivity, orientation tuning, directionality and responsiveness of neurones matured rapidly over this period. The proportions of simple and complex cells were similar in kittens aged 4 weeks or more to those in adult cats, whereas prior to this most neurones that displayed an orientation preference appeared to be immature simple cells. 6. A laminar analysis revealed that very few units in the superficial layers (I, II and III) in area 18 are visually responsive in kittens during their first and second weeks, but orientation selectivity rapidly develops during the third week. By contrast, even in very young, visually inexperienced kittens, the majority of neurones found in deeper laminae (IV, V and VI) are visually responsive and a few of them already show an orientation preference; however, the subsequent appearance of larger proportions of orientation-selective cells in these lower layers is a more prolonged process than in upper laminae.(ABSTRACT TRUNCATED AT 400 WORDS)

Continuity of orientation columns between superficial and deep laminae of the cat primary visual cortex.

1. Recent reports of a marked and consistent dislocation between orientation columns in the superficial and deep layers of cat striate cortex (Bauer, 1982, 1983) directly contradict the traditional view of the system (Hubel & Wiesel, 1962). This has considerable implications for our current understanding of cortical organization, and in order to clarify the issue we have carried out experiments to test the continuity of the columnar system with depth, in central regions of area 17. 2. In twenty-four penetrations, eighteen of which were placed as perpendicular as possible to the surface of the cortex, orientation preference was assessed at regular intervals both qualitatively and using a randomly interleaved quantitative technique. The distribution of preferred orientations was analysed with reference to a detailed histological reconstruction of the electrode track, including the location of laminar boundaries and the course of radial tiers of cells and capillaries. 3. From a further series of eighteen near-perpendicular penetrations, the change in average orientation between one superficial and one deep layer recording site was compared with the deviation of the track from perpendicular to the surface and hence parallel to the orientation columns. 4. In penetrations perpendicular to the surface of the cortex, orientation preference showed little variation between superficial and deep laminae. In oblique penetrations, preferred orientation generally changed according to a single, smooth trend. Those irregularities that were encountered were confined to oblique penetrations, and were distributed throughout the cortical laminae. 5. In conclusion, our evidence does not support the presence of a systematic discontinuity with depth within the orientation columnar system. It is therefore entirely consistent with earlier evidence on the subject.

Organization of neurones preferring similar spatial frequencies in cat striate cortex.

The optimal spatial frequencies were determined for over 300 neurones in cat striate cortex. Neurones recorded within about 100 microns were more likely to have similar optimal spatial frequencies than were neurones recorded at greater separations. But, even neurones recorded close together sometimes differed markedly in their optima; these differences could not be attributed to differences in receptive field eccentricity. When one lamina was sampled more than once, on different electrode penetrations, the different samples of neurones did not often have similar optimal spatial frequencies. To investigate whether neurones in laminae or in columns prefer the same spatial frequencies, data from normal and oblique penetrations were compared. Little difference in the degree of organization was seen in the two kinds of penetrations.

Preferred direction of movement as an element in the organization of cat visual cortex.

Neurones recorded close together in the cat's striate cortex prefer not only the same orientation of elongated visual stimulus but also the same direction of stimulus movement. The degree of similarity in both preferred orientation and preferred direction is greater in electrode penetrations made perpendicular to the cortical surface than in oblique penetrations. This suggests that preferred direction is organized in columnar fashion, just as is orientation.

Functional changes across the 17-18 border in the cat.

Changes in velocity sensitivity, receptive field (RF) position, and RF size were investigated in long oblique penetrations crossing the 17-18 border. The penetrations were histologically reconstructed and the border determined by cytoarchitectonics. In cortex subserving central and paracentral vision change in velocity sensitivity allowed a reasonable physiological identification of the 17-18 border. The physiological border correlates well with the histological border zone, best with its medial edge. Changes in RF position and RF size are of little use for physiological identification of the border in this region. In this cortical region area 18 representation of the vertical meridian (VM) has a high magnification factor. In cortex subserving peripheral vision, the change in velocity sensitivity was small and the change in RF position coincided with the cytoarchitectonics.

The physiological effects of monocular deprivation and their reversal in the monkey's visual cortex.

1. 1127 single units were recorded during oblique penetrations in area 17 of one normal, three monocularly deprived and four reverse sutured monkeys. 2. In all animals most cells outside layer IV c were orientation-selective, and preferred orientation usually shifted from cell to cell in a regular progressive sequence. 3. The presence in layer IV c of non-oriented, monocularly driven units, organized in alternating right-eye and left-eye 'stripes' (LeVay, Hubel & Wiesel, 1975) was confirmed. 4. Early monocular deprivation (2--5 1/2 weeks) caused a strong shift of ocular dominance towards the non-deprived eye. However, even outside layer IV c, neural background and some isolated cells could still be driven from the deprived eye in regularly spaced, narrow columnar regions. In layer IV c the non-deprived eye's stripes were almost three times wider, on average, than the deprived. 5. Later monocular deprivation (11--16 months) had no detectable influence on layer IV c but seemed to cause a small shift in ocular dominance outside IV c. Deprivation for 6 1/4 months in an adult had no such effect. 6. After early reverse suturing (at 5 1/2 weeks) the originally deprived eye gained dominance over cells outside layer IV c just as complete as that originally exercised by the eye that was first non-deprived. 7. The later reverse suturing was delayed, the less effective was recapture by the originally deprived eye. Reversal at 8 weeks led to roughly equal numbers of cells being dominated by each eye; fewer cells became dominated by the newly open eye after reverse suturing at 9 weeks and most of them were non-oriented; reversal at 38 1/2 weeks had no effect. 8. Binocular cells, though rare in reverse sutured animals, always had very similar preferred orientations in the two eyes. The columnar sequences of preferred orientation were not interrupted at the borders of ocular dominance columns. 9. Even within layer IV c there was evidence for re-expansion of physiologically determined ocular dominance stripes. After early reverse suture, stripes for the two eyes became roughly equal in width. Possible mechanisms for these changes are discussed.

A quantitative study of the projection area of the central and the paracentral visual field in area 17 of the cat. I. The precision of the topography.

1. In the course of long oblique penetrations through the postlateral gyrus a variation in the position of the receptive fields (RF-scatter) of single cells recorded extracellularly is observed. This is superimposed on the continuous topological representation of the retina. Spezifying the RF-positions by the azimuthal and elevation coordinates of their geometrical centers, the standard deviation (SD) of the mean RF-positions of cells recorded in 200 mum long horizontal sections of cortex is calculated and the total radial scatter of RF-positions (Sanderson, 1971) as defined: (see article) is determined. The radial scatter is found to have its smallest value (1 degree visual angle (v.a.)) in the projection area of the functional center of the area centralis increasing to 3-4 degrees v.a. at 10 degrees eccentricity. 2. The mean RF-diameter as defined: (see article) is centrally 0.7 degrees v.a. increasing to 2.6 degrees v.a. at 10 degrees eccentricity. The ratio of the largest RF-diameter to the smallest RF-diameter is between 7-9 and remains almost constant over the central 10 degrees of the projection area. The magnification factor (M) as defined: mm Cortex/degree v.a. is centrally 2.3, decreasing paracentrally to 0.6. 3. The cells in area 17 whose RFs have the same direction in the visual field constitute the spatial subunit of the retinocortical projection. The diameter of the spatial subunit is calculated as: (see article). The spatial subunit functionally represents, therefore, that part of the visual field whose location and area is calculated by averaging over the RFs of the individuals of its cell population. It is found that the cells belonging to a spatial subunit are distributed within a cortical cylinder of 2.6-2.8 mm in diameter, the peak of the distribution coinciding with the central axis of the cylinder. 4. Within the projection area of the central 10 degrees of the retina in area 17 the spatial subunits have the same diameter. This suggests that each retinal ganglion cell is functionally connected with an equal number of cells in area 17 irrespective of its position within the retina and that, therefore, the retinocortical projection is organized on the basis of a stereotyped schema if a basic spatial relationship is concerned.

Functional organization of a visual area in the posterior bank of the superior temporal sulcus of the rhesus monkey.

1. Anatomical studies have shown the cortex of the posterior bank of the superior temporal sulcus to receive a projection from visual cortical areas, including areas 17, 18 and 19. In this paper the response of single neurones in this area to simple visual stimulation is reported. Ten monkeys were studied.2. A clear but relatively crude topographic representation of the visual field was found. There was a large variation in the size of the receptive fields of individual cells, even in a single penetration. Some cells, with the central parts of their receptive fields located from between 1 and 5 degrees from the centre of gaze had receptive fields averaging about 10 degrees x 10 degrees or even larger. Other cells with central receptive fields had much smaller field sizes.3. Two main types of neurones were encountered, with subdivisions within each type. The first type responded to movement irrespective of form. These could be subdivided into neurones which responded to movement in any direction within the receptive field and neurones which responded to movement in one direction only (directionally selective neurones). Another type of cell was responsive to both contour and movement, much like the complex and lower order hypercomplex cells. Almost all such neurones were directionally selective.4. In oblique penetrations through this cortical region, there tended frequently to be an orderly shift in preferred directions of motion, thus suggesting the possibility of a columnar organization for movement.5. Combined anatomical (degeneration) and electrophysiological experiments showed that these types of neurones are found in those regions of the posterior bank of the superior temporal sulcus receiving a direct projection from area 17.

Photoelastic analysis of stresses around oblique holes

A three-dimensional photoelastic analysis was conducted to determine the magnitude and distribution of stresses around oblique holes in a uniaxially loaded plate. The holes were circular and inclined at angles of 45 deg and 60 deg with the faces of the plate. The plate-thickness-to-hole-diameter ratiot/D was 2.40. One end of each hole was blended to the face of the plate through a break radius equal to the radius of the hole. The plate dimensions were sufficiently large to simulate conditions of an infinite plate. The plates were loaded perpendicular to the plane of skewness. Stress distributions were obtained on sections perpendicular to the direction of loading. Results point to two critical areas of stress concentration: one at the acute-angle intersection of the hole and the surface of the plate and the other in the break-radius area. The stress concentrations in the latter area reach values of 4.6 and 6.7 compared to 3.6 and 4.5 at the acute-angle intersection, for the inclination angles of 45 deg and 60 deg, respectively. A simplified analysis used for the break-radius area gave results in agreement with the experiment. Thus, it was shown that break radii in oblique penetrations may have deleterious rather than beneficial effects. Comparison of results for the acute-angle intersection with existing theoretical and experimental values shows a definite and pronounced dependence of the stress-concentration factor on thickness-to-diameter ratio.