Contact performance analysis of pressure controller's sealing interface in deep in-situ pressure-preserved coring system

The sealing performance of contact interfaces plays the most important role in the design and operation of the in-situ pressure-preserved coring system.To meet the demand of ultra-high pressure-retained coring for oil and gas exploration in deep reservoirs,a quantitative analysis of the contact mechanical behavior of the pressure controller was performed.Based on the micro-contact theory of rough surfaces,a three-dimensional numerical model of the rough contact interface between the valve cover and the valve seat was constructed,and the micro-contact behavior of the metal contact surfaces was comprehensively studied.The results show that the actual contact area of the valve interface increases with the increase of surface roughness before the critical contact point,but decreases after that.Compared with the real contact model with double rough surfaces,although the simplified hard-contact model with a single rough surface can reflect the micro-contact behavior of the rough surface to a certain extent,it cannot truly reveal the microchannel morphology between the sealing interfaces under pressure.Therefore,the realistic double-rough-surface model should be recommended to evaluate the sealing performance of coring tools,particularly for high pressure conditions.The material properties of valves have a significant effect on the contact characteristics of rough surfaces,which suggested that the actual contact area decreases with the increase of the elastic modulus of the contact material under the same loading conditions.The knowledge of this work could help to enhance the seal design of pressure controllers for in-situ pressure-preserved coring.

Pressure control method and device innovative design for deep oil in-situ exploration and coring

Deep oil exploration coring technology cannot accurately maintain the in-situ pressure and temperature of samples, which leads to a distortion of deep oil and gas resource reserve evaluations based on conventional cores and cannot guide the development of deep oil and gas resources on Earth. The fundamental reason is the lack of temperature and pressure control in in-situ coring environments. In this paper, a pressure control method of a coring device is studied. The theory and method of deep intelligent temperature-pressure coupling control are innovatively proposed, and a multifield coupling dynamic sealing model is established. The optimal cardinality three term PID (Proportional-Integral-Differential) intelligent control algorithm of pressure system is developed. The temperature-pressure characteristic of the gas-liquid two-phase cavity is analyzed, and the pressure intelligent control is carried out based on three term PID control algorithms. An in-situ condition-preserved coring (ICP-Coring) device is developed, and an intelligent control system for the temperature and pressure of the coring device is designed and verified by experiments. The results show that the temperature-pressure coupling control system can effectively realize stable sealing under temperature-pressure fields of 140 MPa and 150 °C. The temperature-pressure coupling control method can accurately realize a constant pressure inside the coring device. The maximum working pressure is 140 MPa, and the effective pressure compensation range is 20 MPa. The numerical simulation experiment of pressure system control algorithm is carried out, and the optimal cardinality and three term coefficients are obtained. The pressure steady-state error is less than 0.01%. The method of temperature-pressure coupling control has guiding significance for coring device research, and is also the basis for temperature-pressure decoupling control in ICP-Coring.

Investigation of magnetization reversal and domain structures in perpendicular synthetic antiferromagnets by first-order reversal curves and magneto-optical Kerr effect

Perpendicular synthetic-antiferromagnet(p-SAF) has broad applications in spin-transfer-torque magnetic random access memory and magnetic sensors. In this study, the p-SAF films consisting of (Co/Ni)3]/Ir(tIr)/[(Ni/Co)3are fabricated by magnetron sputtering technology. We study the domain structure and switching field distribution in p-SAF by changing the thickness of the infrared space layer. The strongest exchange coupling field(Hex) is observed when the thickness of Ir layer(tIr) is 0.7 nm and becoming weak according to the Ruderman–Kittel–Kasuya–Yosida-type coupling at 1.05 nm,2.1 nm, 4.55 nm, and 4.9 nm in sequence. Furthermore, the domain switching process between the upper Co/Ni stack and the bottom Co/Ni stack is different because of the antiferromagnet coupling. Compared with ferromagnet coupling films, the antiferromagnet samples possess three irreversible reversal regions in the first-order reversal curve distribution.With tIrincreasing, these irreversible reversal regions become denser and smaller. The results from this study will help us understand the details of the magnetization reversal process in the p-SAF.

One-stage coclear implantation via a facial recess approach in children with otitis media with effusion

Objective:To investigate surgical indications, operative techniques, complications and auditory and speech rehabilitation for cochlear implant (CI) in children with otitis media with effusion (OME). Material and methods:This is a retrospective review of records of 24children with bilateral profound sensorineural hearing loss and OME who were implanted during January 2011 to November 2014 in the Department of Otorhinolaryngology and Head and Neck Surgery at the PLA Hospital, using one-stage implantation via the facial recess approach and round window insertion. The incus was removed in 8 cases during the implantation procedure. Local infiltration of dexamethasone and adrenaline in the middle ear was also performed. Postoperative complications were examined. Preoperative and postoperative questionnaires including Categories of Auditory Performance (CAP), Speech Intelligibility Rating (SIR), and the Meaningful Auditory Integration Scale (MAIS) were collected. Results: All electrodes were implanted successfully without any immediate or delayed complications. Inflammatory changes of middle ear mucosa with effusion were noted in all implanted ears. The scores of post-implant CAP and SIR increased significantly in all 24 cases (t ? ?25.95 and ?14.09, respectively for CAP and SIR, p<0.05). Conclusions:One-stage CI via the facial recess approach with round window insertion is safe and effective in cochlear implant candidates with OME, as seen in the 24 children in our study who achieved improved auditory performance and speech intelligibility after CI. Copyright ? 2015, PLA General Hospital Department of Otolaryngology Head and Neck Surgery. Production and hosting by Elsevier (Singapore) Pte Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Characteristics of central visual field defect after macular hole surgery

AIM: To investigate the characteristics of postoperative central visual field defect(cVFD) in patients with macular hole(MH).METHODS: Eighteen eyes from 18 MH patients were involved in this retrospective study which reviewed square root of loss variance(sLV) and mean defect(MD) of the visual field test in all subjects. The relationship between cVFD and MH stage, as well as the postoperative ellipsoid zone disruption were evaluated using Spearman's correlation test. RESULTS: Our analysis determined Spearman coefficient is 0.705 for the correlation between sLV and MH stage(P<0.01), 0.877 for the correlation between sLV and postoperative ellipsoid zone disruption(P<0.01) and 0.721 for the correlation between MD and postoperative ellipsoid zone disruption(P<0.01). A significant relationship was also detected between postoperative ellipsoid zone disruption and MH stage(r=0.470, P<0.05). Univariate regression analysis indicated that sLV and MD were associated with postoperative ellipsoid zone disruption(P<0.01, P<0.01, respectively). CONCLUSION: Postoperative cVFD is highly correlated with MH stage and postoperative ellipsoid zone disruption in patients with MH.

A numerical study of hydrodynamic influence on collision of brash ice with a structural plate

The ice-structure collision is a transient process, which is further complicated by the presence of the water. It remains unclear how important the hydrodynamic influences are during the collision. This problem is partially investigated in this paper using numerical methods. To simplify the problem as much as possible without loss of generality, a short ice cylinder of circular section is assumed to collide with a vertical large structure plate under a variety of collision scenarios. Among them the most important cases are: (1) the rigid ice cylinder collision with the rigid or elastic structural plate at different collision velocities, (2) the elastic ice cylinder collision with the rigid or elastic structural plate at different collision velocities and (3) the elastoplastic ice cylinder collision with the rigid or elastic structural plate at different collision velocities. The numerical results show that: (1) the hydrodynamic influences are negligible in the first case, (2) the hydrodynamic influences in the second and third cases are not negligible, and become very significant in the third case. The influences are numerically estimated to be in the range of 20%–60% in terms of the momentum change. If the ice response is approximately decomposed into the rigid-body motions and the deformation modes at the instant of the collision with the structure, the previous conclusions show that the hydrodynamic influences on the rigid-body motions of the ice are negligible, but those on the elastic and elastoplastic modes of the ice are significant. Comparison with the case of a submerged ice cylinder (although not a practical case) reveals that the hydrodynamic influences are small in the first case due to the fact that the energy loss is used to produce the water splash and the cavity behind the ice cylinder. Through this study we come into the conclusion that the hydrodynamic influences are not important for the rigid-body motions, but important for the elastic or elastoplastic modes.

Long-term safety and absorption assessment of a novel bioresorbable nitrided iron scaffold in porcine coronary artery

This study aimed to investigate the long-term biocompatibility, safety, and degradation of the ultrathin nitrided iron bioresorbable scaffold (BRS) in vivo, encompassing the whole process of bioresorption in porcine coronary arteries. Fifty-two nitrided iron scaffolds (strut thickness of 70 μm) and 28 Vision Co–Cr stents were randomly implanted into coronary arteries of healthy mini-swine. The efficacy and safety of the nitrided iron scaffold were comparable with those of the Vision stentwithin 52 weeks after implantation. In addition, the long-term biocompatibility, safety, and bioresorption of the nitrided iron scaffold were evaluated by coronary angiog-raphy, optical coherence tomography, micro-computed tomography, scanning electron microscopy, energy dispersive spectrometry and histopathological evaluations at 4, 12, 26, 52 weeks and even at 7 years after im-plantation. In particular, a large number of struts were almost completely absorbed in situ at 7 years follow-up, which were first illustrated in this study. The lymphatic drainage pathway might serve as the potential clearance way of iron and its corrosion products.