Resistance Of Sheath Research Articles

Analysis for metal sheath corrosion rate in AC high voltage power cable

Reliable power transmission requires the safe operation of high-voltage cable. A number of high-voltage cable failures caused by aluminium sheath corrosion has been reported these years. However, neither discussion on factors influencing corrosion rate nor specification describing corrosion inhibiting method has been presented. Thus, it is crucial to address the research gap in evaluating corrosion rate of aluminium sheath in various corrosive environments. Here, the effect of chlorides on aluminium sheath corrosion is analyzed. Using scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), the corroded surface is investigated. Titration experiment is performed to quantify the chlorides content in buffer layer of cable. Polarization curves are employed to analyze the corrosion rate of aluminium sheath in different chlorides content environment. Surface analysis result shows that chlorine-rich phase can be observed on the corroded surface. Titration experiment result reveals that buffer layer used in high voltage cable is one of the sources of chlorides content which varies from 0.7 to 4.2 wt%. Finally, polarization curve shows that when chloride content increases from 0.6 to 1.8 wt%, the pitting potential left shifts from −0.689 to −0.742 V. The corrosion resistance of aluminium sheath deteriorates significantly with the increase of chlorides content.

Characteristic Analysis of the Outer Sheath Circulating Current in a Single-Core AC Submarine Cable System

The single-core alternating current (AC) submarine cable can be provided with an outer sheath that is firmly grounded on both ends of the cable. The circulating currents of the outer sheath are generated to be almost as large as the conductor current. The outer sheaths, which have different structures and properties, generate unwanted losses, asymmetric distribution of circulating current, and extra heat in the single-core AC submarine cables. The formation mechanism of the circulating currents in the submarine cable sheath and armoring is analyzed from the perspective of electromagnetic shielding using electromagnetic transient theoretical analysis, simulation calculation, and field experiments. Equations for calculating the circulating currents of the sheath and armoring are proposed, and influences of these relationships that include the different material characteristics of the sheath and armoring are analyzed. The influence factors, which include different levels of magnetic armoring permeability, resistivity, and ground resistance of the outer sheath, can affect the symmetrical distribution of the circulating current in the outer sheaths. We propose using the phase differences to determine the material properties of each metallic section in the submarine cable.

Pemilihan Kabel Instalasi Listrik Untuk Bangunan Gedung Berdasarkan Kualitas Tahanan Isolasi

The building fire in Pontianak was the result of an electrical short circuit or an electric current, namely the connection between a live conductor and a neutral conductor. Where the electrical installation cables used are generally NYM and NYA cables.
 NYM and NYA cables must be of good quality. This is related to the safety of buildings against fire hazards due to short circuits of electrical cables. For this reason, research is needed in the form of measuring cable insulation resistance to ensure the quality and feasibility of several cable brands on the local market in Pontianak.
 Based on the measurement results on the five test samples, each cable NYM 3 x 2.5 mm2, NYM 2 x 2.5 mm2 and NYA 2.5 mm2, it was found that the NYM cable was 3 x 2.5 mm2 (sample A), NYM cable 2 x 2 .5 mm2 (Sample A) and 2.5 mm2 NYA Cable (sample B) have the highest insulation resistance of the cable sheath compared to 4 (four) other samples, namely 25,010 M Ohm (NYM 3 x 2.5 mm2), 25,425 M Ohm ( NYM 2 x 2.5 mm2) and 39,850 M.Ohm (NYA 2.5 mm2). This shows that these cables have a better quality of sheath insulation resistance than others. While the cables that have the smallest sheath insulation resistance are 11,014 M Ohm (Sample B NYM cable 3 x 2.5 mm2), 10,720 M Ohm (Sample B NYM cable 2 x 2.5 mm2) and 21,580 M.Ohm (Sample A NYA 2.5 mm2) cable.

Stent coating by electrospinning with chitosan/poly-cyclodextrin based nanofibers loaded with simvastatin for restenosis prevention

The main cause of failure of angioplasty stenting is restenosis due to neointimal hyperplasia, a too high proliferation of smooth muscle cells (SMC). The local and sustained delivery of selective pleiotropic drugs to limit SMC proliferation seems to be the hopeful solution to minimize this post surgery complication. The aim of this study is to develop a stent covered by nanofibers (NFs) produced by electrospinning, loaded with simvastatin (SV), a drug commonly used for restenosis prevention. NFs were prepared from the electrospinning of a solution containing SV and a mixture of chitosan (cationic) and β-cyclodextrin (CD) polymer (anionic) which form together a polyelectrolyte complex that makes up the NFs matrix. First, the SV/CD interactions were studied by phase solubility diagram, DRX and DSC. The electrospinning process was then optimized to cover a self-expandable NiTiNOL stent and the mechanical resistance of the NFs sheath upon its introduction inside the delivery catheter was considered, using a crimper apparatus. The morphology, coating thicknesses and diameters of nanofibers were studied by scanning electron microscopy. The SV loading rates on the stents were controlled by the electrospinning time, and the presence of SV in the NFs was confirmed by FTIR. NFs stability in PBS pH 7.4 buffer could be improved after thermal post-treatment of NFs and in vitro release of SV in dynamic conditions demonstrated that the release profiles were influenced by the presence of CD polymer in NFs and by the thickness of the NFs sheath. Finally, a covered stent delivering 3 µg/mm2 of SV within 6 h was obtained, whose efficiency will be investigated in a further in vivo study.

Influence of thermal contact resistance of cementing interface on radial heat transfer in wellbore

ABSTRACT The wellbore injected with heating fluid requires temperature field prediction to formulate production strategy. The classical radial heat transfer calculation of wellbore takes into account the thermal conductivity resistance of casing, cement sheath and formation, ignoring the “Thermal Contact Resistance” caused by the micro-annulus at the cementing interface. In order to study the influence of micro-annulus on radial wellbore temperature field prediction, the calculation method of thermal contact resistance of micro-annulus at the cementing interface filled with gas was deduced. And then it was verified by the experimental equipment and specimens of casing, cement sheath and formation. Finally, the thermal contact resistance was introduced into the “overall heat transfer coefficient” to study the deviation of the classical method in predicting the wellbore temperature field. The results show that, if the interfacial thermal contact resistance isn’t considered, under the conditions of the roughness of micro-annulus increases (0.01 mm ~ 1 mm), the time of steam injection increases (2 d ~ 40 d), the temperature of injected steam increases (500 K ~ 700 K), and the temperature of formation increases (300 K ~ 400 K), the calculated inner wall temperature of the cement sheath will be relatively high (1 K ~ 3 K), and the outer wall temperature will be relatively low (4 K ~ 9 K), while the inner wall temperature of the formation is relatively much high (28 K ~ 38 K). Moreover, the change of these conditions has little influence on the deviation. The research in this paper proves that the micro-annulus at the cementing interface has a great influence on the radial wellbore temperature prediction. The calculation method used can make the prediction more in line with the actual situation, thus making the production dynamic analysis and method optimization more effective.

Thermal conductivities and thermal runaways of superconducting MgB2 wires stabilized by an Al + Al2O3 sheath

This paper presents a study of the thermal transport properties of extra-light MgB2/Ti/Al + Al2O3 composite wires. The longitudinal thermal conductivity has been investigated as a function of temperature and magnetic field on wires differing only by an outer Al + Al2O3 sheath. The correlation between the thermal transport properties, the microstructure of the Al + Al2O3 sheath and the Al/Ti interface reactions provide important information for these thermally stabilized extra-light superconductors. The thermal runaways observed by the current–voltage characteristics of MgB2/Ti/Al + Al2O3 wires correlate well with the conductor’s temperature affected by the thermal conductivity and the resistance of the outer sheath.

Simulation of electrical discharge in a 3.6 Joule miniature plasma focus device using SIMULINK

A novel technique has been developed and studied in this paper to simulate the electrical discharge circuit of a 3.6 J miniature plasma focus device (PFD) and investigate the effect of inductance variation on voltage spike and current dip. The technique is based on a correlation between the electrical discharge circuit and plasma dynamics in a very small PFD that operates at the energy of 3.6 J. The simulation inputs include the charging voltage, capacitor bank capacitance, current limiter resistance, by-pass resistance as well as the time-dependent inductance and resistance of the plasma sheath which are calculated by assuming the plasma dynamics as transit times in going from one phase to the next. The variations of the most important elements in the circuit (i.e. the constant and breakdown inductances) and their effects on the current dip are studied in PFDs with low and high constant inductance. The model demonstrated for achieving a good pinch in the PFD, although the total inductance of the system should be low; however there is always an optimum inductance which causes an appropriate pinch. Furthermore, the electrical power produced by the pulsed power supply, the mechanical energy as well as the magnetic energy which are transferred into the plasma tube were obtained from simulation. The graph of electrical power demonstrated a high instantaneous increment in the power transferred into the plasma as one of the greatest advantages of the pulsed power supply. The simulation was performed using software tools within the MATLAB/SIMULINK simulation environment.

Tissue Dissection before Direct Manipulation to the Pathology with Pulsed Laser-Induced Liquid Jet System in Skull Base Surgery

Background: Most difficulties in skull base tumor removal are generally caused by adhesion of feeding arteries to the vital structures and cranial nerves. Water jet technology provides tissue dissectability with preservation of fine blood vessels. However, problems are still remaining whether tumor removal with preservation of peripheral nerve function is possible or not. This investigation evaluated functional preservation of peripheral nerves and dissectability with newly developed pulsed laser-induced liquid jet (LILJ) system under intraoperative electrophysiological monitoring. Methods: The LILJ system was used to treat 21 patients with skull base tumor manifesting as severe visual disturbance. Intraoperative visual evoked potential (VEP), and pre/postoperative conventional visual assessments were investigated. Results: Precise dissections of the tumor were obtained, resulting in gross-total removal in 19 of 21 patients. Two patients with meningiomas with tight adhesion to lenticulostriate arteries had small remnants. Overall 16 of the 21 patients showed immediate improvement on VEP, 2 had no change, and 3 had prolonged latency, which required intermittent suspension of procedure. A total of 20 patients and 40 eyes showed good recovery at discharge, and all patients evaluated had recovered good visual status. Conclusions: The LILJ system can achieve safe and optimal removal with functional preservation of optic nerves, probably because of the high resistance of the arachnoidal sheath.

Tissue dissection before direct manipulation to the pathology with pulsed laser-induced liquid jet system in skull base surgery—preservation of fine vessels and maintained optic nerve function

Most difficulties in skull base tumor removal are generally caused by adhesion of feeding arteries to the vital structures and cranial nerves. Water jet technology provides tissue dissectability with preservation of fine blood vessels both in experimental and clinical situations. However problems still remain regarding whether tumor removal with preservation of peripheral nerve function is possible or not. This clinical investigation evaluated functional preservation of peripheral nerves and dissectability with a newly developed pulsed laser-induced liquid jet (LILJ) system under intraoperative electrophysiological monitoring. The LILJ system was used to treat 21 patients with skull base tumors manifesting as severe visual disturbance through the extended transsphenoidal approach. The LILJ system consists of a bayonet-shaped catheter incorporating a jet generator, and total weight is around 7 g. Intraoperative visual evoked potential (VEP), and pre/postoperative conventional visual assessments were investigated. Precise dissections of the tumor were obtained, resulting in gross total removal in 19 of 21 patients. Two patients with meningiomas with tight adhesion to the origin of the lenticulostriate arteries had small remnants. Of the 21 patients, 16 showed immediate improvement on intraoperative VEP, 2 had no change, and 3 had prolonged latency, which required intermittent suspension of procedure. A total of 20 patients and 40 eyes showed good recovery at discharge, and all patients evaluated had recovered good visual status. The LILJ system can achieve safe and optimal removal with functional preservation of optic nerves, probably because of the high resistance of the arachnoidal sheath and fine vascular tissue.

Effect of finite electrode area ratio on high-frequency Langmuir probe measurements

Langmuir probe (LP) measurement generally requires a reference electrode with large surface area compared with that of a probe. Whereas a reference electrode with large surface area is available in laboratory experiments, surface area of the reference electrode is limited when the probe is installed on a small spacecraft such as a sounding rocket. Insufficient electrode area ratio of the reference electrode to the probe leads to distortion of the current–voltage (I–V) characteristics and therefore the derived electron temperature and density might be erroneous. In order to investigate the effect of finite electrode area ratio on LP measurements, we have carried out a laboratory simulation by setting up a model sounding rocket with whole apparatus for LP measurement in a vacuum chamber. By changing the frequency of sweep voltage applied to the probe from 0.1 Hz to 3 kHz, we have derived an equivalent resistance and capacitance of the reference electrode sheath, which was thought to be the principal cause of distortion in I–V characteristics. The result shows that when the electrode area ratio is 124, the electron temperature is unaffected by the impedance of the reference electrode while the electron density is underestimated by 50%. In addition, the high sweep frequency method introduced here turned out to be an effective approach to make measurements with LP possible even when a sufficient surface area ratio cannot be achieved.

Energy Transformations in Column of Plasma-Focus Discharges With Megaampere Currents

Energy transformations are estimated from experimental results obtained on the PF-1000 plasma focus facility operated with a deuterium gas filling and maximum current of 2 MA, which enabled the neutron yield of >; 1011 to be obtained. Use was made of the laser interferometry images and the recorded signals of hard X-rays (HXRs) and neutrons, as well as voltage, current, and current-derivative waveforms. The calculations of the inductance, derivative of inductance, and resistance of the current sheath enabled the evaluation of energy delivered to the plasma. It was estimated that, during the intensive pulses of the HXRs and neutrons, energy of 3-11 kJ is delivered to the plasma column probably through an anomalous resistance at the time closely before and during pulses of HXR and neutron production. A predominant portion of this energy is effectively used for the acceleration of fast deuterons capable of producing fusion neutrons.

Tensile Properties of Optical Fiber Irradiated by Low Voltage Electron Beam Homogeneously

Homogeneous low voltage electron beam irradiation (HLEBI) with small dose of 0.30 to 1.17 MGy enhanced the elasticity indicated by the initial and maximum slope values of stress–strain curves ((dσ/dε)i and (dσ/dε)max) of 250 µm diameter optical fiber (OF), which was constructed with both core (10 µm diameter) and clad (125 µm diameter) silica glasses covered with acryl-urethane sheath (62.5 µm thickness). The highest (dσ/dε)i and (dσ/dε)max values of 5.3 and 5.9 GPa, which were about 10 and 20% higher than those (4.8 and 4.9 GPa) before irradiation, were found at 0.104 MGy, respectively. Moreover, remarkable effects of HLEBI of 0.65 MGy on both tensile strength (σf) and fracture strain (εf) of OF were obtained at each fracture probability (Pf) value. Since HLEBI also enhanced the density of dangling bonds of each material of OF, effects of compressive stress on pull-out resistance and elasticity enhancements of fiber and sheath probably occurred. Thus, 0.64 MGy-HLEBI enhanced the (dσ/dε)i and (dσ/dε)max as well as εf, resulting in enhancement of σf of OF.

Resistance to Motion of Flexor Tendons and Digital Edema: An In Vivo Study in a Chicken Model

Tissue edema contributes to resistance to motion of flexor tendons during postsurgical exercises. We assessed edema formation and resistance of injured subcutaneous tissue and sheath to motion of the digital flexor tendon in a chicken model. Ninety-four toes of 47 white Leghorn chickens were divided into 6 surgical groups and 1 nonsurgical control. Subcutaneous tissue and the sheath were incised, and the skin incision and the subcutaneous tissue were closed surgically. The toes were evaluated morphologically for severity of edema and tested for the force and work required to move the tendon. The evaluation time points were 1, 2, 3, 4, 5, and 7 days after surgery. Edema in the toes was scored according to severity and extent. The force and energy required to move the tendon were measured at the first and sixth cycles after cyclic loading in a testing machine with customized software and were statistically analyzed. The force and work increased progressively for the first 4 days, and were relatively consistent from days 4 to 7. The severity of edema peaked at the third and fourth days. At each postsurgical day, edema scores corresponded to increases in the force and work. The force and work were reduced drastically (30%-50%) after the first 6 cycles of toe motion. Resistance to tendon motion increased for the initial 4 days after surgery and remained comparatively consistent from the fourth to the seventh days. The severity of digital edema peaks at the third and fourth postoperative days. Motion of the digits for several cycles greatly reduces the resistance to the subsequent movement. We believe that tendon mobilization should not necessarily be started within the initial postoperative days, the optimum time to begin probably is the period from the fourth to the seventh day after surgery, and that judgment of edema helps to determine how aggressive exercise should be.

Resistência de cultivares de arroz a Rhizoctonia solani e Rhizoctonia oryzae

Isolados de Rhizoctonia solani e Rhizoctonia oryzae, agentes causais da queima-da-bainha e mancha-da-bainha, respectivamente, foram coletados em lavouras de arroz irrigado no Estado do Tocantins. O objetivo deste trabalho foi avaliar a resistência de 12 cultivares de arroz a essas doenças, sob condições artificiais de inoculação, em casa de vegetação. Não houve correlação entre resistência das cultivares a R. oryzae e R. solani quanto ao comprimento da lesão na bainha infectada pelo método de palito de dentes. A relação entre tamanho da lesão na bainha e folha foi linear e significativamente negativa (r = -0,66, P<=0,05), indicando que não há relação entre resistência das cultivares na bainha e nas folhas a R. solani. Entre as cultivares precoces, Labelle apresentou maior grau de suscetibilidade em todos os métodos de inoculação. A área sob a curva de progresso da doença baseada na altura da lesão no colmo e o método de inoculação utilizando casca e grão de arroz foram mais adequados para a determinação da resistência entre as cultivares. Diferenças significativas entre as cultivares de ciclo médio não foram observadas. As folhas apresentaram resistência à infecção por R. oryzae nos testes de inoculação utilizando discos de micélio.

Two switch high voltage modulator for plasma-based ion implantation

A new pulse modulator for plasma-based ion implantation (PBII), which is adaptable for a wide range of the load impedance has been developed, using a newly-set closing switch, which is set in parallel with the target and grounded chamber. In this article, time evolutions of the voltage applied to a target and current through the target for a conventional modulator with only a main switch, are presented, where the diameter of a disk target and the target position from the plasma source are varied. The output impedance of the modulator changes the rise time of the applied voltage due to the charging of the stray capacitor in the circuit. At the end of the target voltage, the stray capacitor begins to discharge to the equivalent resistance of the ion sheath. This brings a decay of the target voltage with a time constant consisting of the total capacitance and the sheath resistance. For the newly-developed modulator, the output impedance of the modulator was low enough to decrease the rise time of the target voltage. The sheath-capacitance was shortened by a new closing switch to promote the discharge. Due to both the low output impedance of the modulator and a newly-set closing switch, the modulator output voltage can be transferred to the target as a load without change of the waveform.

Influence of Plasma Resistance and Fluctuation on Probe Characteristics in Detached Recombining Plasmas

In order to find the causes of the strong anomaly of current-voltage characteristics of Langmuir probe observed in detached recombining plasmas in a linear divertor plasma simulator, NAGDIS-II, we have investigated plasma resistance along a magnetic field and potential fluctuations in the detached recombining plasmas. Simple calculation on the ratio between the plasma length, at which plasma resistance and resistance of ion sheath formed around a probe tip become equal, and an electron collection length indicates that the evaluation of electron temperature Te becomes inaccurate at Te of less than 0.6 eV when plasma density and neutral pressure are 1.0 × 1018 m—3 and 10 mtorr, respectively. The potential fluctuation in detached recombining plasmas was found to be so large compared to Te/e, which can also modify the probe characteristics.

Extraction of migrated self-expanding esophageal metal stents

Background: When self-expanding metal stents are used in the palliative treatment of malignant stenoses complications can occur and require the endoscopic extraction of the stent. Methods: Three Gianturco-Z stents and two EsophaCoil stents had to be extracted because of migration (4 patients) and strangulation of healthy esophageal tissue between the coil loops during EsophaCoil stent release (1 patient). Because of the strong expansion force of the Gianturco-Z stent, the plastic sheath of a polypectomy snare was replaced by the steel sheath of a basket used for mechanical lithotripsy of bile duct stones. The sufficient resistance of the steel sheath allowed the stents to be compressed. The EsophaCoil stents were gradually retracted with a polypectomy snare over a plastic tube. Results: All stents could be extracted successfully. There were no severe complications related to extraction. Conclusion: By means of the endoscopic extraction techniques described above, it is possible to safely remove self-expanding esophageal stents.

Conduction block in acute and chronic spinal cord injury: different dose-response characteristics for reversal by 4-aminopyridine.

The effect of the potassium channel blocker, 4-aminopyridine (4-AP), on conduction of action potentials in injured guinea pig spinal cord axons was measured using isolated tracts in oxygenated Krebs' solution at 37 degrees C. The dose-response characteristics of acutely and chronically injured axons were compared. The maximal improvement of conduction occurred in acutely injured axons at a concentration of 100 microM 4-AP, but in chronically injured spinal cord at 10 microM. The threshold for significant response to 4-AP was between 0.5 and 1 microM in chronically injured cords, and between 1 and 10 microM following acute compression injury. The difference in susceptibility to potassium channel blockade may be related to underlying differences in the mechanism of conduction block at the two stages of injury. Initially, junctions between axons and myelin are acutely disrupted, altering primarily the leakage resistance of the myelin sheath and periaxonal space. In chronically injured cords, there is widespread but incomplete process of repair in the lesion site, which leaves many axons partially myelinated. The difference in sensitivity to 4-AP suggests there is also some modification of the accessibility of axonal potassium channel or a change in their affinity for the drug.

Effects of paranodal potassium permeability on repetitive activity of mammalian myelinated nerve fiber models

Almost all potassium channels within mammalian myelinated nerve fibers are covered by the myelin sheath and their majority is concentrated in a small paranodal region. In order to investigate effects of this paranodal potassium permeability on nerve fiber behavior via a simulation approach, a myelinated fiber model is required that treats myelin sheath and internodal axolemma as separate entities. Such a fiber description was developed by Blight (1985) and his model was used to investigate the effects paranodal potassium channels have on the ability of maintaining repetitive firing in response to a constant current injected into the fiber. It was found that increasing the potassium channel density at the paranode from low to moderate values widened the range of injected currents with a repetitive response. This promotion of repetitive activity by the introduction of additional potassium channels occurred up to an "optimal" value beyond which a further increase in paranodal potassium permeability narrowed the range of currents with a repetitive response. Finally, if a certain limit in paranodal potassium channel density was exceeded, repetitive activity was abolished completely. These results were obtained regardless of the assumptions about the electrical resistance of the myelin sheath. On the other hand, in the absence of potassium channels repetitive firing could be observed only when a high resistance myelin sheath was assumed, whereas a nerve fiber model with electrical properties inferred from intracellular recordings needed at least some potassium channels within the paranodal region for repetitive firing in response to an injected current.

Promoting Effect of n-Decylmethyl Sulfoxide on the Penetrability of the Optic Nerve for Lidocaine HCI in Cats

We examined the effect of n-decylmethyl sulfoxide (n-decyIMSO) on the resistance of the optic nerve sheath to the penetration of lidocaine hydrochloride. Three series of experiments were carried out in living cats, administering lidocaine with and without n-decyIMSO. The visual evoked potential (VEP) and optic nerve response (ONR) were measured. The results obtained indicated that n-decyIMSO increased the penetration of lidocaine. The presence of lidocaine (1%) and n-decyIMSO (2.5%) decreased the ONR amplitude from 120 to 15 μV after a time lag of 105 min, and VEP decreased from 9.0 to 5.5 μV. This effect was preserved during the experiment. Histological examination showed only minimal changes in the optic nerve and the eye globe and its contents. Some infiltration of mononuclear cells was found around the optic nerve sheath.