BI-QUAD DUAL REFLECTOR ANTENNA FOR WLAN TASKS

Рассматривается двухрефлекторная Bi-Quad антенна, способная работать в диапазоне частот, соответствующих WLAN Wi-Fi 2,4 ГГц. Благодаря возможности управления положением рефлекторов удается добиться изменения направления излучения, что повышает эффективность использования антенны, коэффициент направленного действия. При управлении происходит поворот ячеек, из которых сформированы отражательные структуры, что позволяет пропускать электромагнитное излучение, которое формирует излучатель из медного провода в форме цифры «восемь». Предложенная конструкция позволяет обеспечить три стабильных режима работы антенны: двустороннее излучение, когда оба рефлектора в открытом положении, при таком режиме у антенны наблюдается одинаковое излучение в обоих направлениях с равным КНД; излучение вверх, в данном режиме верхний рефлектор открыт, что приводит к свободному протеканию электромагнитных волн, а от закрытого нижнего происходят отражения, в результате этого происходит увеличение КНД антенны по сравнению с ситуацией двустороннего излучения; аналогичная ситуация происходит при излучении вниз, когда открыт нижний рефлектор, так электромагнитные волны отражаются от закрытого верхнего рефлектора вниз, что приводит к увеличению КНД антенны. Предложенная конструкция обладает высокой эффективностью в диапазоне рабочих частот The article discusses a two-reflector Bi-Quad antenna capable of operating in the frequency range corresponding to WLAN Wi-Fi 2.4 GHz. Thanks to the ability to control the position of the reflectors, it is possible to achieve a change in the direction of radiation, which increases the efficiency of using the antenna, and increases the directivity. During control, the cells are rotated, from which the reflective structures are formed, which allows the transmission of electromagnetic radiation, which is formed by the emitter, formed from a copper wire in the shape of the number "eight". The proposed design makes it possible to provide three stable modes of antenna operation: double-sided radiation, when both reflectors are in the open position, in this mode the antenna has the same radiation in both directions with equal directivity; radiation upward, in this mode, the upper reflector is open, which leads to free flow of electromagnetic waves, and reflections occur from the closed lower reflector, as a result of this, the antenna directivity increases in comparison with the situation of two-sided radiation. A similar situation occurs when radiating downward, when the lower reflector is open, so electromagnetic waves are reflected from the closed upper reflector downward, which leads to an increase in the antenna directivity. The proposed design is highly efficient in the operating frequency range

Design of an Anti-Slip Mechanism for Wheels of Step Climbing Robots

This manuscript presents a shape memory alloy (SMA) actuated anti-slip mechanism for the wheels of step climbing robots. The proposed mechanism comprises three kinematic chains considering the Lazy Tong and the bi-stable four-bar mechanism. Chain 1 of the mechanism is used to clamp on the edges of the stairs to avoid slipping. The second chain of the mechanism is used to switch the mechanism between two stable positions, i.e., open position and closed position, of chain 1. For activating the mechanism, the third chain is employed which is based on SMA wire. Furthermore, the mechanism is designed to achieve passive switching from the open position to the closed position. Equations are developed to determine the dimensions of various members. Using those parameters, a 3D model of the proposed mechanism is developed. Stress analysis is performed and the model is found to be safe under a load of 250 N with a factor of safety of 3.025. The mechanism is attached to either side of a wheel of the outer radius of 290 mm. To analyze the kinematics of the mechanism, a three-dimensional model in MSC Adams is developed and studied. The force required by SMA actuator is found to be less than 5 N. The proposed mechanism may be used for various unmanned robotic systems while mitigating step-like obstacles in the path.

Successful Intervention of Coiled Tubing Rugged Tool with Real-Time Telemetry System in Saudi Arabia First Multistage Fracturing Completion with Sand Control System

An openhole multistage completion required selective fracture stimulation, flow control, and sand control in each zone. An openhole multistage completion was designed by combining a production sleeve integrated with sand screens and inflow control devices and a fracture sleeve with high open flow port. The system was designed to use a ball drop to isolate the bottom intervals while fracturing upper intervals. After fracture stimulation, the fracture seat/ball needed to be milled. The production sleeve were designed to be shifted to the open position and the fracturing sleeve to the closed position through mechanical shifting tool to put the well on production. The fracturing sleeve and the production sleeve were located close to each other and a successful shifting operation needed an appropriate shifting tool, with a real-time downhole telemetry system that met the temperature limitations while providing accurate depth control, differential pressure readings, and axial force (tension and compression) measurements. Hydraulic-pressure-activated shifting tools were used to manipulate the sleeves. A coiled tubing (CT) rugged downhole tool with real-time telemetry was used to run the shifting tools. Yard tests were conducted to identify the optimum rates and pressures to actuate the hydraulically activated shifting tools and study their behavior. The expansion of the fracturing sleeve shifting tool keys initiated at 1.6 bbl/min (400 psi) and the keys were fully expanded at 1.8 bbl/min (600 psi), whereas the expansion of production sleeve shifting tool keys initiated at 0.3 bbl/min (700 psi), and the keys were fully expanded at 0.4 bbl/min (900 psi). During the design and planning of the shifting operation, simulations were conducted, and surface and downhole tools were selected carefully to ensure the CT could provide enough downhole upward force (5,000 to 6,000 lbf) to close the fracture ports and 2,000 to 4,000 lbf to open production sleeves. Following the fracturing operation, the first CT run aimed to mill fracture seats/balls to clear the path for the subsequent shifting operation. In the second CT run, all the fracturing sleeves were shifted to the closed position while production sleeves were shifted to the open position. The CT rugged downhole tool proved critical for depth correlation and accurate placement of the shifting tools. The real-time downhole acquisition of differential pressure across the toolstring also allowed operating the shifting tools under optimum conditions, while downhole force readings of tension and compression confirmed the shifting of completion accessories. Two fracturing sleeves were shifted to the closed position at 2.4 bbl/min and 700-psi downhole differential pressure, with the downhole weights of 700 lb and 1,000 lbf. Three production sleeves were shifted to open position at 0.6 bbl/min and 1,200-psi downhole differential pressure, and the maximum surface and downhole weights recorded were 73,000 lb and 19,200 lb, respectively. That operation led to sand-free production and confirmed the success of the first multistage completion enabling fracturing operation and controlling sand production in Saudi Arabia. This study describes the use of real-time downhole measurements and their significance when surface parameters do not give clear indication of shifting. It also features the first-time use of two hydraulically activated shifting tools operated during the shifting operation in Saudi Arabia's first multistage completion enabling fracturing operation and controlling flow/sand production.

FONEM KONSONAN DAN VOKAL BAHASA BALI DI KABUPATEN TABANAN: KAJIAN DIALEKTOLOGI STRUKTURAL

This study aims to investigate the phonological variations of the Balinese language in Tabanan Regency and to map them. Observations were made in four villages, namely Bongan, Berembeng, Sanda, and Wangaya Gede. Data were collected by using interview and observation methods.The data are swadesh words spoken by the informants during the interview. The results obtained were that the phoneme /ə/ in the final open position has two realizations, namely [a] and [ə]. Each sound has a different area. [ə] found at the observation point 1,2,4 and [a] found at the observation point 3. The phoneme /e/ at the open end position has two variations, namely [e] and [ε], while the phoneme /o/ realized by [o] and [ɔ]. [e] and [o] were found at the observation point 1,2 4, while [ε ] and [ɔ] were found in TP 3. In addition, there was also difference in the realization of the /k/ consonant phoneme. The phoneme /k/ is realized by [k] and [?]. [k] was used in TP3, while [?] used in TP 1,2,4. In TP 1,2,4 there was not phoneme /a/ in the final distribution, while TP 3 has a complete /a/ distribution. Areas that have a complete phoneme /a/ distribution, [ə] would not be found in the final distribution. In areas where the phoneme /a/ has incomplete distribution, [ə] has a complete distribution there. [k] in the final distribution was unknown at TP3, but known in TP 1,2,4. Meanwhile [?] in the final distribution was known merely in TP 1,2,4 but not in TP 3. Keywords: phoneme; consonant; vowel; Dialectology

Long Lasting Reversibility of the Mitochondrial Permeability Transition in Saccharomyces cerevisiae

The Saccharomyces cerevisiae mitochondrial unspecific pore (ScMUC) is an uncoupling unspecific pore that shares some similarities with the mammalian permeability transition pore (mPTP). When open, both channels deplete ion and proton gradients across the inner mitochon-drial membrane. However, the role of mPTP is to reversibly open to protect cells against stress. If mPTP remains stuck in the open position the cell dies. In contrast, ScMUC is probably dedicated to deplete oxygen from the medium in order to kill competing organisms. Such O2 depletion would be better achieved if oxidative phosphorylation is at least mildly uncoupled. Still, when oxida-tive phosphorylation is needed ScMUC should be able to close. To test this, the reversible opening and closing of ScMUC in the presence of different effectors was tested in isolated mitochondria from S. cerevisiae. Evaluations were conducted at different incubation times, monitoring the rate of O2 consumption, mitochondrial swelling and the transmembrane potential. It was observed that ScMUC did remain reversibly open for minutes. A low energy charge (ATP/ADP) closed the chan-nel. In addition, high Ca2+ promoted closing and it was a highly powerful effector.

Valvular prostheses

Prosthetic heart valves may be mechanical or bioprosthetic. Mechanical valves, which are composed primarily of metal or carbon alloys, are classified according to their design as ball-caged, single-tilting-disc, or bileaflet-tilting-disc valves. In ball-cage valves, the occluder is a sphere which is contained by a metal ‘cage’ when the valve is in its open position, and fills the orifice when the valve is in its closed position. In single-tilting-valves, the occluder is a single circular disc which is constrained in its motion by a cage, a central strut, or a slanted slot in the valve ring, therefore it opens at an angle less than 90° to the sewing ring plane. In bileaflet-tilting-disc valves there two occluders, two semicircular discs that open forming three orifices, a central one and two lateral ones. Biological tissue valves prostheses may be heterografts, which are composed of porcine, bovine, or equine tissue (valvular or pericardial), or homografts, which are preserved human aortic valves. Heterografts include stented and stentless bioprostheses. In stented valves, the biological tissue of the valve is mounted on a rigid stent (plastic or metallic) covered with fabric. Conversely stentless bioprostheses use the patient’s native aortic root as the valve stent. The absence of a stent and sewing ring cuff make it possible to implant a larger valve for a given native annulus size, resulting in a larger effective orifice area (EOA).

A Numerical Study on the Flow Characteristics According to the Operating Speed of Hollow Jet Valve

Various types of valves are installed in the emergency discharge facility of dams, and when water is discharged in an emergency, vibration may occur in the valve depending on operating conditions. In this study, for the hollow jet valve, which is frequently used in the emergency discharge facility of dam, the flow phenomenon occurring according to the operating speed of the valve was observed and the vibration characteristics according to the operating speed were investigated through CFD.In particular, when the hollow jet valve is closed, the valve casing is opened while the inside of the valve casing is filled with air, and the open position is also changed during the opening time, thus the calculation was performed using the unsteady 2-phase overset mesh technique.As a result of calculation through CFD, it was found that when the operating speed of the hollow jet valve was changed, the time range of vibration appeared differently, and the value of the drag coefficient generated was also changed. In addition, it was found that the location of vibration generated according to the operating speed is generated at mostly identical locations, the cause of the vibration is not the vibration caused by the hydraulic pressure exiting the hollow jet valve, and it can be seen that the atmosphere outside the valve flows into the valve casing, creating a complex flow phenomenon inside the valve casing and acting as the cause of vibrating the hollow jet valve.

Deployable space grids with lockable joints

The use of deployable structures in architecture began in the 1960s, based on the pioneering work of Emilio Pérez Piñero. It has had an interesting development using bundle or scissor modules, but with solutions that are always based on through-bolted joints. In this document, a new system for deployable space grids is proposed. This new system is based on the use of self-lockable joints, opening up a new and interesting field of design possibilities. The resulting space grids can be deployed by means of joints arranged on the bars that have a self-locking mechanism which is engaged in the final open position. This configuration overcomes the significant buckling that is characteristic of deployable structures with through-bolted joints. Different solutions are proposed for various uses, and the data from the theoretical and experimental analysis are provided.

Forex Data Analysis using Weka

This paper conducts some experiments with forex trading data. The data being used is from kaggle.com, a website that provides datasets for machine learning and data scientists. The goal of the experiments is to know how to design many parameters in a forex trading robot. Some questions that want to be investigated are: How far the robot must set the stop loss or target profit level from the open position? When is the best time to apply for a forex robot that works only in a trending market? Which one is better: a forex trading robot that waits for a trending market or a robot that works during a sideways market? To answer these questions, some data visualizations are plotted in many types of graphs. The data representations are built using Weka, an open-source machine learning software. The data visualization helps the trader to design the strategy to trade the forex market.