Perforation Channels Research Articles

Elastosis perforans serpiginosa induced byd‐penicillamine treated with cyclosporine and allopurinol

Elastosis perforans serpiginosa (EPS) is a rare condition within the group of perforating dermatoses. It is characterized by the synthesis of anomalous elastic fibers that are eliminated through perforating channels (transepidermal elimination). It is classified into three subtypes. One of them is drug-induced by prolonged treatment with d-penicillamine. This drug is a heavy metal chelator used to treat diseases such as rheumatoid arthritis, cystinuria, and Wilson's disease. Years of treatment with d-penicillamine at high doses are required for developing EPS, with occasional slow regression after drug withdrawal. There is no established treatment for EPS, with described cases using various treatment options such as corticoids, retinoids, tazarotene, cryotherapy, imiquimod, photodynamic therapy, electrosurgery, and CO2 laser among others with inconsistent results. We present a case of EPS induced by d-penicillamine with favorable response to cyclosporine and allopurinol in a patient with a history of Wilson's disease since childhood. They maybe considered as possible therapeutic options not described so far for an entity with variable response to current treatments. We highlight the extensive involvement of the case with progression, despite the suspension of d-penicillamine and failure to previous treatments with photodynamic therapy and retinoids.

Оценка динамики фильтрационных процессов в перфорационных каналах ствола горизонтальных скважин сложной геометрии

Оценка динамики фильтрационных процессов в перфорационных каналах ствола горизонтальных скважин сложной геометрии

The Influence of the Characteristics of the Gas Reservoirs Perforation-Entering on the Well Production Capabilities

The main complications in the production of residual gas from depleted gas reservoirs are characterized. The deterioration of the formation pay zone in the depleted reservoirs occurs mainly due to the accumulation of liquid and particles and due to possible deformation of the rocks. One of the methods to reduce the effect of the for-mation bottom-hole zone contamination on the productive characteristics of wells is to create perforation tunnels in the bottomhole zone that can pass through the contaminated zone and improve the hydrodynamic connection of the gas-bearing reservoir with the well. The author studies the effect of the number and the size of perforation tun-nels (depending on the permeability of the reservoir at constant wellhead pressure) on the gas-well flow rate. The research results are presented in the form of graphical dependence of the ratio between the flow rate of the well with perforation channels and a hydrodynamically perfect well q/q0 on determining factors, as well as in the form of graphic relationships among individual determining factors. Using the research results, it is found that the ra-tional value of the diameter of the perforation channels should be at least 0,03 m, the channel lengths should not be shorter than 0,292-0,307 m and the number of channels per meter of the revealed reservoir thickness should be not less than 17-19 depending on the permeability of the formation. The number of perforation tunnels and their length de-crease with the growth of reservoir permeability according to the exponential law.

Preparation and evaluation of novel multi-channel orally disintegrating tablets

In this study, novel orally disintegrating tablets (ODTs) with multi-channel structure were designed to provide a rapid disintegration and subsequently drug dissolution. The ODTs were prepared using conventional wet compression through perforating channels with a special multi-channel mold. A modified sieve method was used in disintegration test as a quick screening tool during formulation evaluation. Moreover, physical properties, in vitro and in vivo disintegration time, dissolution rate and mouthfeel were also evaluated. The results demonstrated that developed multi-channel ODTs had good physical parameters, in vitro/in vivo correlation (IVIVC) of disintegration time and acceptable mouthfeel and dissolution. It also revealed that the presence of channels could accelerate the disintegration of ODTs because the channels could shorten the distance of water penetration and increased the specific surface area, resulting in a significant reduction in disintegration time. Above all, the introduction of novel multi-channel ODTs provided an alternative preparation method for ODTs and achieved good disintegration characteristics.

ПРОГНОЗИРОВАНИЕ РИСКОВ ЗАКЛИНИВАНИЯ ДЛЯ ИСКЛЮЧЕНИЯ ВОЗМОЖНОСТИ ПРИХВАТОВ ТЕХНИЧЕСКОЙ СИСТЕМЫ «ПЕРФОБУР» ПРИ БУРЕНИИ РАЗВЕТВЛЕННЫХ КАНАЛОВ В ТЕРРИГЕННЫХ КОЛЛЕКТОРАХ

Актуальность. Одним из перспективных методов вторичного вскрытия продуктивных пород является бурение глубоких каналов малого диаметра технической системой радиального бурения «Перфобур». Рассмотрены вопросы прогнозирования и предупреждения прихватов бурильных компоновок технической системы вследствие возможного заклинивания в интервалах неустойчивых пород. Заклинивания в данных интервалах с большой степенью вероятности происходят вследствие упруговязкопластического деформирования поперечного сечения перфорационного канала. Цель: оценка рисков прихватов технической системы «Перфобур» вследствие заклинивания при бурении и спускоподъемных операциях и разработка технологических мероприятий по их предупреждению. Объекты: глубокий канал малого диаметра и сверхмалого радиуса кривизны в терригенном пласте-коллекторе нефтяного месторождения в Поволжье, представляющего собой чередование аргиллита, алевролита и песчаника. Методы: геомеханическое моделирование, численное интегрирование, метод переменных модулей. Результаты. Определены перемещения стенок глубокого перфорационного канала во времени для терригенного пласта-коллектора, представляющего собой чередование аргиллита, алевролита и песчаника. Получены зависимости упруговязкопластического перемещения стенок канала малого диаметра (58–60 мм) и радиуса кривизны (5–10 м) с изменением зенитного угла. Упруговязкопластическое перемещение верхней стенки перфорационного канала, как правило, значительно (в 1,5 и более раза) превышает упруговязкопластическое перемещение боковой стенки перфорационного канала. Следовательно, упруговязкопластическое перемещение верхней стенки является наиболее опасным и определяющим с точки зрения заклинивания особенно при спускоподъемных операциях. При бурении долотами типа PDC (опасное перемещение стенки равно 2 мм) определено, что наиболее опасным с точки зрения заклинивания является пропласток аргиллита и время безопасного ведения работ составляет один час. Для предупреждения возможного заклинивания компоновок технической системы «Перфобур» предложено применение специально разработанного секционного винтового забойного двигателя габарита 49 мм с кинематическим отношением рабочих органов – 9:10, что кратно увеличивает механическую скорость бурения по сравнению ранее применяемыми (также не серийными) винтовыми забойными двигателями с кинематикой рабочих органов – 5:6, использование струйных и волновых кольмататоров, расширителей, калибраторов-виброгасителей и осцилляторов, размещаемых в расчетных местах компоновки низа бурильной колонны для предотвращения и ликвидации возможных осложнений в радиальных каналах.

Thermal/Mechanical Interaction in Laser Perforation Process: Numerical-Model Buildup and Parametric Study

Summary In this paper, a generic thermal/mechanical interaction model was developed to predict the penetration rate and mechanical damage around perforation tunnels that resulted from the laser perforation of rock samples. The perforating process is driven by heat emitted by a laser beam directed at the surface of a sample. The temperature propagation, thermal expansion, and thermal/mechanical interaction were modeled by coupling heat conduction in solid media with the elastic/plastic constitutive mechanical response of rocks. The phase changes that occur during the melting and evaporating process were accounted for in the latent heat of fusion and of vaporization. The heating boundary was updated dynamically along with the evolution of perforation channels. The model was used to parametrically investigate the effects of material properties, stress ratio, and laser–beam characteristics on the penetration rate and mechanical damage.

Channelled tablets: An innovative approach to accelerating drug release from 3D printed tablets

Conventional immediate release dosage forms involve compressing the powder with a disintegrating agent that enables rapid disintegration and dissolution upon oral ingestion. Among 3D printing technologies, the fused deposition modelling (FDM) 3D printing technique has a considerable potential for patient-specific dosage forms. However, the use of FDM 3D printing in tablet manufacturing requires a large portion of polymer, which slows down drug release through erosion and diffusion mechanisms. In this study, we demonstrate for the first time the use of a novel design approach of caplets with perforated channels to accelerate drug release from 3D printed tablets. This strategy has been implemented using a caplet design with perforating channels of increasing width (0.2, 0.4, 0.6, 0.8 or 1.0mm) and variable length, and alignment (parallel or at right angle to tablet long axis). Hydrochlorothiazide (BCS class IV drug) was chosen as the model drug as enhanced dissolution rate is vital to guarantee oral bioavailability. The inclusion of channels exhibited an increase in the surface area/volume ratio, however, the release pattern was also influenced by the width and the length of the channel. A channel width was ≥0.6mm deemed critical to meet the USP criteria of immediate release products. Shorter multiple channels (8.6mm) were more efficient at accelerating drug release than longer channels (18.2mm) despite having comparable surface area/mass ratio. This behaviour may be linked to the reduced flow resistance within the channels and the faster fragmentation during dissolution of these tablets. In conclusion, the width and length of the channel should be carefully considered in addition to surface area/mass when optimizing drug release from 3D printed designs. The incorporation of short channels can be adopted in the designs of dosage forms, implants or stents to enhance the release rate of eluting drug from polymer-rich structures.

Influence of Morphology on Flow Law Characteristics in Open-Cell Foams: An Overview of Usual Approaches and Correlations

Foam structures have been a subject of intensive research since the last decade. The pore space in open-cell foam is interconnected, forming perforated channels of varying cross-sectional areas where fluid can flow. Knowledge of pressure drop induced by these foam matrices is essential for successful design and operation of high-performance industrial systems. In this context, analytical correlations were derived for the determination of Darcian permeability (KD) and Forchheimer inertia coefficient (CFor) in open-cell foams of different strut shapes. It has been shown that the flow law characteristics are strongly dependent on strut shape, strut characteristic dimension, and length. The applicability of new correlations was examined by comparing and validating the numerical and experimental flow law characteristics data against the predicted ones. An excellent agreement has been observed for the foam structures of different materials and variable texture in a wide range of porosity and Reynolds number.

Hydraulic fracturing process by using a modified two-dimensional particle flow code - case study

By using a modified PFC2D model, the authors conducted a series of simulations to examine the influences of in-situ stress ratio, fluid injection rate, anisotropy of laminated rocks, and perforation parameters on hydraulic fracturing process. The simulations indicated that: 1) larger in-situ stress ratio will induce smaller breakdown pressures and faster propagation, and hydraulic fractures will extend along the direction of the maximum principal stress or approach to this preferred path; 2) smaller difference of in-situ stresses or faster fluid injection rate is helpful for creation of complex fracture network; 3) weak layers are preferred locations and directions for fracture initiation and propagation in the laminated rocks; 4) hydraulic fractures initiate easily at the bottoms of perforation channels, and propagate generally along or approaching to the direction of maximum principal stress.

Review of Experimental Studies of Cold-Formed Steel Channels with Slotted Webs under Bending

The paper presents a review of experimental studies of cold-formed steel channels with perforated webs under bending. In the experimental studies five channels were tested under four-point bending and two channels were subject to a uniformly distributed load. A distortional buckling failure was observed in the tested channels. The flexural strength of the tested perforated channels was calculated using the direct strength method equations and compared with the test results. The direct strength method equations for beams with holes allowed to define precisely the flexural strength of the slotted channels for specimens tested under four-point bending.

Stability Behavior of Perforated Lipped Channel Columns

Taking the cold-formed thin-walled perforated lipped channels with simple edge stiffeners and complex edge stiffeners as research objects. The influence of perforated parameters, such as hole width, hole height, hole shape and hole spacing, on axial compressive bearing capacity and buckling mode of these two types of lipped channels were studied by finite element analysis. It shows that the change of hole width, hole shape and hole spacing may change the buckling mode, but influence little on ultimate bearing capacity within a reasonable perforated range; However, it indicates that the ultimate bearing capacity decreased obviously with the opening height increased. The suggestions on reasonable hole shape and hole size were put forward. Furthermore, combined the direct strength method of lipped perforated channels under axial compression abroad with the relevant specification of our country, the direct strength method of lipped perforated channel columns for our country were put forward also. Then, the methods mentioned above were extended to calculate the ultimate bearing capacity of perforated channels with complex edge stiffeners under axial compression, and the validity of the formulas was verified.

(Invited) Power Loss Reduction in Perforated-Channel HFET Switches

The key factors affecting the efficiency of power electronic systems are the conduction and switching losses in semiconductor power switches. For field-effect transistor switches, the conduction power loss is proportional to the product of the squared current, ION , flowing through the switch in the on-state and the switching loss is proportional to the squared maximum switch voltage, VMAX, the effective device output capacitance, COUT , and the switching frequency, fSW . Therefore, the RONCOUT product is an important figure of merit of a FET-type switch determining the overall power efficiency. Our proposed and implemented Perforated Channel (PC) FET design 1 allowed us to significantly reduce RON , but not COUT. We now propose and demonstrate the improved PC-HFET design that allows us to reduce both RON and COUT . This design reduces the power losses and significantly improves the efficiency of power electronics systems. In the PC-HFET, the portions of the channel under the gate are removed and the remaining channel forms a dash-line of islands WG1 wide with WGG spacing between them. The channel “filling factor” in PC-HFET is kF = WG1/(WG1+WGG ). Compared to conventional HFET with the same total width W, the total channel width and, hence, the device gate capacitance, of the PC-HFET is kF times smaller. However, our analytical estimates, numerical simulations (using the 3D simulation in Synopsys Sentaurus device simulator), and experimental data all show the on-resistance of the PC-HFET can be only 10-15% higher than that of the conventional HFET of the same width. This is achieved due to a strong current spreading effect in the source-to-gate and, especially, in a larger gate-to-drain spacing. The gate capacitance of PC-HFET reduces proportionally to the kF factor as proven by our simulations and experimental data presented in [1]. However our 3D simulations show that the CGD scaling in PC-HFET at high drain voltage is nearly the same as that for conventional HFET. To reduce this capacitance, we proposed the PC-HFET device design with the holes extending into the gate-drain spacing. Our simulations show that the hole extension allows for nearly the same CGD reduction as the gate metal removal over the holes. We used the obtained RON and CGD data to calculate the power loss in AlGaN/GaN PC-HFET and showed that the PC-HFET design filling factor kF = 0.25 reduces the total conversion loss in the power switch by more than a factor of 2. [1] G. Simin, M. Islam, M. Gaevski, J. Deng, R. Gaska, and M. Shur, “Low RC-constant Perforated-Channel HFET”, IEEE El. Dev. Letters, V. 35, pp.449-451, 2014 Figure 1

Mechanism and Application Effect of Compound Perforation Fracturing Technology in Low Permeability Reservoir

Compound perforation fracturing technology is a space combination type ultra-deep perforating that can overcome some flaws conventional perforation has, such as shallow penetration and compaction damage. It can remove the compaction band and near wellbore pollution in rock matrix which results from conventional perforation. This paper introduces the theory of effect and influence factor of compound perforation fracturing technology and summarize the advantages for low permeability gas well on the basis of analyzing the mechanism of action about increase production of compound perforation. In order to evaluate the effects of application of this technology in in low permeability reservoir, 11 compound perforation wells and 12 conventional perforation wells were selected which have the similar physical property and the evaluation was conducted in two blocks. The results show that compound perforation can make the formation fracture pressure decrease in 3~5MPa and increase the permeability near the perforation channel. This technology has better effects than the conventional and decrease the cost effectively, improving production in low permeability oil and gas field.

New Approaches to Realizing High Power Nitride Based Field Effect Transistors

We report on several key innovations to enable high performance/high reliability of nitride based FETs that include (1) the use of Perforated Channel (PC) design; (2) surface application of Low Conducting Layers (LCLs); (3) the combination of these two approaches (for achieving the ultimate power performance at the highest switching frequencies with minimum losses); (4) novel device geometries (combining the best features of lateral and vertical devices for normally-off transistors); (5) improved control of self-heating and better heat dissipation. We also review our recent results exploring the PC channel and LCL designs . Our experimental and simulation results demonstrated a sharp increase in the breakdown voltage, a large enhancement of the cutoff frequency, a better device stability and smaller spreading of the device parameters for higher yield, improved manufacturability, and smaller self-heating due to a lower thermal impedance.

New Approaches to Realizing High Power Nitride Based Field Effect Transistors

High breakdown voltage, excellent current carrying capabilities, high electron saturation velocity, high mobility, good thermal properties, chemical inertness, and radiation hardness of nitride semiconductors make them uniquely suited for high power applications. However, new approaches are needed to achieve their full potential. We report on several key innovations that include (1) the use of Perforated Channel (PC) design (to control and minimize the parasitic and on resistances and off and on transistor capacitances for faster switching and sharply reduced losses); (2) surface application of Low Conducting Layers (LCLs) (to control the properties and stability of ungated surfaces and dramatically increase the breakdown voltage); (3) the combination of these two approaches (for achieving the ultimate power performance at the highest switching frequencies with minimum losses); (4) novel device geometries (combining the best features of lateral and vertical devices for normally-off transistors with unprecedented power handling capability); (5) improved control of self-heating and better heat dissipation using the PC channel design. We also review our recent results exploring the PC channel and LCL designs [1-3]. These experimental and simulation results demonstrated a sharp increase in the breakdown voltage, a large enhancement of the cutoff frequency, a better device stability and smaller spreading of the device parameters for higher yield, improved manufacturability, and smaller self-heating due to a lower thermal impedance.[[1]] G. Simin, M. Islam, M. Gaevski, J. Deng, R. Gaska, and M. Shur, “Low RC-constant Perforated-Channel HFET”, IEEE Electron Device Letters, 35 (2014)[2] M. Gaevski, Jianyu Deng, A. Dobrinsky, R. Gaska, M. Shur, and G. Simin, Static and transient characteristics of GaN power HFETs with low-conducting coating, physica status solidi, Article first published online: 24 MAR 2014 | DOI: 10.1002/pssc.201300541[3] G Simin, M Shur, R Gaska, Semiconductor device with low-conducting buried and/or surface layers - US Patent Application 20,130,126,905 (2013)

73 Retrograde Wiring of Collateral Channels of the Heart in Chronic Total Occlusions: A Systematic Review and Meta-analysis of Safety, Feasibility and Incremental Value in Achieving Revascularisation

Background and aimsIncreasingly collateral channels have been used for retrograde wiring as a means of improving success rates in the recanalisation of complex CTOs.However the feasibility of wiring variable collateral...

Low RC-Constant Perforated-Channel HFET

The novel HFET design using perforated channel region under the gate reduces drain and source parasitic resistances due to the current spreading effect in the source-gate and gate-drain regions. Demonstrated results for AlGaN/GaN HFET show that the RONCG time constant reduces around two times using simple and robust perforated channel device processing. These results are especially important for new generations of power switching transistors.

Reconstructive Surgery in the Lower Urinary Tract in Children: Can the Complication Rate Be Reduced?

Objective: Reconstructive surgery of the lower urinary tract in children is reported with a high complication rate. The aim was to evaluate the complication rate at our institution. Material and methods: Between 2000 and 2010, 41 boys and 19 girls were consecutively operated on with augmentation with ileum (45), alternative CIC-channel (57) and bladder neck plasty (42) in isolation or as combined procedures in individuals with neurogenic bladder dysfunction NBD (42), bladder exstrophy-epispadias complex BEEC (13), isolated epispadias IE (2) and posterior urethral valves, PUV (3). Median age at surgery was 11 years (range 1.3 -21) and median follow-up time 7 years (1 -10). Complications were consecutively observed at follow-up according to a structured protocol. As first line care, specially trained nurses followed the patients and daily bladder irrigation was included in the CIC follow-up regimen. Results: In individuals with augmentation with ileum, of which all but one performed CIC through an alternative channel, there were stones reported in 3/45 (7%), perforation in 2/45 (4%), reoperation of CIC channel in 5/57 (9%), bowel obstruction in 3/56 (5%) and rupture of BNP in 3/39 (8%). Re-augmentation was not needed and malignancy not found. No significant difference was seen between patients with NBD and BEEC/IE. Conclusion: Complication rates were among the lowest reported for stones, perforation and reoperations of CIC channels and were average for bowel obstruction. Bladder stones and perforation were seen in individuals with bad compliance to recommended CIC-and irrigation regimens.

D-Penicillamine induced elastosis perforans serpiginosa with involvement of glans penis

Elastosis perforans serpiginosa (EPS) is an unusual perforating disorder characterized by extrusion of altered elastic fibers through the epidermis. Clinically, it presents as keratotic papules with a tendency for serpiginous or annular distribution that most commonly involves the sides of the neck and the back. However, involvement of the penis has rarely been reported. We present a case of EPS involving the neck, axilla, and glans penis in a 42-year-old man who had received long-term d -penicillamine treatment for Wilson disease. Skin biopsy revealed perforating channels containing numerous altered elastic fibers, with a characteristic “bramble brush” or “lumpy-bumpy” appearance as demonstrated by an elastin stain. The latter is thought to be pathognomonic for penicillamine-induced degenerative elastosis. These degenerative changes occurring in glans penis have rarely been described in the literature. Prompt recognition of the rare presentation could lead to early discontinuation of the offending drug, to prevent further sequelae.

3D Modeling of Fracture Initiation From Perforated Noncemented Wellbore

Summary A 3D numerical model of fracture initiation from a perforated wellbore in linear elastic rock is developed, which allows one to determine the fracture-initiation pressure (FIP) and the location and direction of an initial rupture. The model assumes that the fracture initiates at the point at which the local maximal tensile stress exceeds the rock tensile strength. The 3D boundary-element method (BEM) is used for stress analysis. The model aims to predict the location of initial fractures and the difference in FIP between different perforation intervals in arbitrarily oriented noncemented wellbores. There are many practical applications for this knowledge, but of particular interest for this research is the employment of differently oriented perforations for creating heterogeneity of FIP between wellbore intervals in multistage fracturing treatment. This can enable stimulation of these intervals in a sequential mode and significantly simplify current treatment diversion and completion practices. Comprehensive analysis revealed that the main parameter that can be used for controlling FIP during multistage fracturing treatment is the angle between the direction of the perforation channel and the preferred fracture plane (PFP). The model allows obtaining the range of the angles that is the most suitable for designing and implementation of diversion between the perforated wellbore intervals. The influence of geometrical parameters of perforation (such as length, diameter, and shape) on FIP is substantially less. In addition, we found that against all expectations, increase of perforation diameter can result in higher FIP. It was also discovered that the influence of the intermediate in-situ stress on FIP is comparable with the effect of perforation misalignment, especially in the situation of a horizontal wellbore and properly aligned perforations. On the basis of the model developed, an approximate approach to the evaluation of the effect of wellbore cementation on fracture initiation was suggested. It was discovered that taking into account the state of stress within the cement before well pressurization can result in both an increase and a reduction of FIP, depending on the parameters of perforating and the wellbore orientation. The presented model is a necessary step toward predictable and controllable fracture initiation, which is vital for multistage-fracturing-treatment diversion.