Small Slot Research Articles

Compact Multiband Microstrip Printed Slot Antenna Design for Wireless Communication Applications

In this paper, a compact multiband printed antenna is proposed to cover four resonant bands in the range of 1-6 GHz. The antenna structure is inspired from that of the classical multi-cavity magnetron resonator. The antenna comprises a slot annular ring structure in the ground plane of an Isola FR4 substrate having Ԑr = 3.5 and thickness h=1.5 mm. The outer circle of the annular ring is loaded with radial arranged small circular slots. On the opposite side of the substrate, the antenna is fed with a 50-Ohm microstrip line. To investigate the effect of different antenna elements on the antenna performance, a parametric study is conducted. The antenna is simulated, fabricated, and measured. The simulated 10 dB return loss bandwidths for the four resonant bands are 35% (1.53–2.11GHz), 14% (2.9–3.34GHz), 12% (4.2–4.75GHz), and 9% (4.94–5.39GHz), respectively. Thus, the antenna is a proper candidate for many in use bands of wireless systems (1.65, 3.14, 4.44, 5.24 GHz), including LTE-FDD, GNSS, GSM-450, W-CDMA/HSPA/k, 802.11a, and IEEE 802.11ac WLAN. The results indicate that the designed antenna has quad-band resonant responses with substantial frequency ratios of f4/f3, f3/f2 and f2/f1. Besides, the antenna offers reasonable radiation characteristics with a gain of 2.5, 4.0, 6.2, and 4.2 dBi, throughout the four resonant bands.

A Metamaterial based Monopole antenna for Satellite based Navigation Applications

A metamaterial-based monopole antenna which resonates at L (L1 and L5) and S band for the IRNSS applications is described. The antenna has a low profile and is nearly is four times smaller in size than a conventional patch antenna. The multifrequency behavior is realized using a reactively loaded structure for the monopole antenna resulting in operation at both monopole and dipole modes. The monopole resonates at S Band and the dipolar mode resonance at L5 band. The novelty of the configuration is in realizing an additional band by introducing small square slot in the loaded structure. Copper wires are used to balance the current between the two ground at the antenna and the CPW feed line. The performance of the antenna is evaluated using ANSYS HFSS.

A Metamaterial based Monopole antenna for Satellite based Navigation Applications

A metamaterial-based monopole antenna which resonates at L (L1 and L5) and S band for the IRNSS applications is described. The antenna has a low profile and is nearly is four times smaller in size than a conventional patch antenna. The multifrequency behavior is realized using a reactively loaded structure for the monopole antenna resulting in operation at both monopole and dipole modes. The monopole resonates at S Band and the dipolar mode resonance at L5 band. The novelty of the configuration is in realizing an additional band by introducing small square slot in the loaded structure. Copper wires are used to balance the current between the two ground at the antenna and the CPW feed line. The performance of the antenna is evaluated using ANSYS HFSS.

Hierarchical Resource Allocation in Multi-Service Wireless Networks With Wireless Network Virtualization

To balance the contradiction between the rapid growth of data service demands and the limited spectrum resources, wireless network virtualization (WNV) has been proposed as a promising technology by isolating and sharing wireless resources among different virtual networks in the future wireless networks. In this paper, a two-dimension-time-scale hierarchical resource allocation scheme is proposed in the multi-service wireless virtualized network, which consists of three 5G generic scenarios. The resource slicing problem is decomposed into two time scales including large time period for inter-slice resource pre-allocation and small time slot for intra-slice resource scheduling. In large time period, the inter-slice resource pre-allocation problem is formulated as a multi-objective optimization problem (MOOP) by modeling the packets arriving and serving process of each slice as a queueing system. While in small time slot, the resource block (RB) and power scheduling in each slice is formulated as a stochastic optimization problem considering dynamic traffic arrivals and time-varying channel conditions, which is aimed at optimizing the overall performance subject to various quality of service (QoS) requirements such as network stability, delay, reliability, transmission rate and power constraints. The stochastic optimization problem can be transformed into a delay-aware optimization problem by applying Lyapunov optimization technique, and be solved by the proposed algorithm consisting of a heuristic algorithm and a concave optimization algorithm. The simulation results show that the proposed schemes are close to the optimal solution with a lower complexity, which can also achieve a performance-delay tradeoff related to the control factor.

High precision strike point control to support experiments in the DIII-D small angle slot divertor

Improvements in strike point control enabled tests with the new small angle slot (SAS) divertor installed at DIII-D with precision as tight as ±1 mm, barring brief perturbations from ELMs. Aside from being narrower than previous baffle structures in DIII-D, simulations indicate that performance of the SAS divertor should be very sensitive to strike point position, making the improved strike point control essential for experiments with the SAS divertor. Improved control entails regulating more divertor geometry target locations than before and setting higher gain on the strike point target. This is achieved by tasking more poloidal field (PF) shaping coils with divertor topology control, fine tuning of the coil configuration and algorithm gains, and adding regulation of the power supply common rail. The result is that although more variables are controlled, precision is better: high frequency jitter in the strike point position is lower on average compared to related discharges with standard divertor shape control.

Wearable Slot Antenna for Biomedical Applications: Mutual Coupling and External Interference

A small slot antenna has desirable characteristics for radio communications and location of an internal transceiver in-vivo medical applications. The effect of coupling between two identical antennas on the human torso was measured between 2.1 GHz antennas on the skin surface. The effect of an external field was measured as a function of the angle in the horizontal plane to quantify noise isolation. The perimeter separation loss was approximately 0.25 dB/mm. The external radio source induces currents in the soft conducting tissue resulting in a sinc radiation pattern for the antenna/body combination with a front-to-back ratio of approximately 12 dB. As the UHF band is commonly used in many non-medical applications, there is concern that external radio sources can result in a reduced signal to noise ratio and perturbed field strength measurements on the skin.

Improved core-edge compatibility using impurity seeding in the small angle slot (SAS) divertor at DIII-D

Impurity seeding studies in the small angle slot (SAS) divertor at DIII-D have revealed a strong relationship between the detachment onset and pedestal characteristics with both target geometry and impurity species. N2 seeding in the slot has led to the first simultaneous observation of detachment on the entire suite of boundary diagnostics viewing the SAS without degradation of core confinement. SOLPS-ITER simulations with D+C+N, full cross field drifts, and n–n collisions activated are performed for the first time in DIII-D to interpret the behavior. This highlights a strong effect of divertor configuration and plasma drifts on the recycling source distribution with significant consequences on plasma flows. Flow reversal is found for both main ions and impurities affecting strongly the impurity transport and providing an explanation for the observed dependence on the strike point location of the detachment onset and impurity leakage found in the experiments. Matched discharges with either nitrogen or neon injection show that while nitrogen does not significantly affect the pedestal, neon leads to increased pedestal pressure gradients and improved pedestal stability. Little nitrogen penetrates in the core, but a significant amount of neon is found in the pedestal consistent with the different ionization potentials of the two impurities. This work demonstrates that neutral and impurity distributions in the divertor can be controlled through variations in strike point locations in a fixed baffle structure. Divertor geometry combined with impurity seeding enables mitigated divertor heat flux balancing core contamination, thus leading to enhanced divertor dissipation and improved core-edge compatibility, which are essential for ITER and for future fusion reactors.

Fragmentation metrics and fragmentation-aware algorithm for spectrally/spatially flexible optical networks

Spectrally/spatially flexible optical networks (SS-FONs) are a promising solution to future traffic requirements in optical backbone networks. SS-FONs exploit the spatial dimension to increase the network capacity, while preserving the resource management flexibility, as they still operate within a flex-grid composed of small frequency slots (slices). A flex-grid makes it possible to realize transmission using super-channels (SChs) that comprise a set of contiguous slots. In this paper, we focus on spectral SChs, i.e., a SCh realized only on one spatial mode on each fiber. In SS-FONs, setting up and tearing down multiple lightpath requests within a flex-grid may result in spectrum fragmentation and, in turn, blocking of requests. In this work, we investigate several fragmentation metrics in a SS-FON. The problem of identifying appropriate metrics to measure fragmentation has been investigated in single-core elastic optical networks, but to the best of our knowledge, there is no such research available for SS-FONs. Therefore, we propose several fragmentation metrics for SS-FONs. We introduce the concept of bordering super-channels (B-SChs), i.e., SChs whose spectrum is allocated at the border of already allocated spectrum slots, which show promising results with regard to minimizing fragmentation. The investigation of all candidate B-SChs allows us to find the one that minimizes the network fragmentation and, in turn, spectrum waste. Hence, we propose a fragmentation-aware (FA) algorithm with bordering SChs that assigns optical resources to dynamic requests by utilizing information from the proposed fragmentation metrics and the set of candidate B-SChs. Experiments on a representative network topology show that the investigation of multiple B-SChs in the FA algorithm reduces the blocking probability when compared to the reference FA algorithms. Finally, we analyze the impact of a spatial continuity constraint on the network fragmentation.

Effects of the Impeller Blade with a Slot Structure on the Centrifugal Pump Performance

An impeller blade with a slot structure can affect the velocity distribution in the impeller flow passage of the centrifugal pump, thus affecting the pump’s performance. Various slot structure geometric parameter combinations were tested in this study to explore this relationship: slot position p, slot width b1, slot deflection angle β, and slot depth h with (3–4) levels were selected for each factor on an L16 orthogonal test table. The results show that b1 and h are the major factors influencing pump performance under low and rated flow conditions, while p is the major influencing factor under the large flow condition. The slot structure close to the front edge of the impeller blade can change the low-pressure region of the suction inlet of the impeller flow passage, thus improving the fluid velocity distribution in the impeller. Optimal slot parameter combinations according to the actual machining precision may include a small slot width b1, slot depth h of ¼ b, slot deflection angle β of 45°–60°, and slot position p close to the front edge of the blade at 20–40%.

Simulation of droplet ejection based on electromechanical parameters & chemical condition for controlling inkjet printing devices

In this study, the droplets in inkjet printing have been simulated based on mechanical parameters including temperature and pressure changing and also the chemical condition contain dielectric of various solvent materials has been investigated. Basically in viewpoint of electromechanical parameters we simulated and divided the inkjet printing into the piezoelectric type and thermal type, and as our results shows, each type has advantages and disadvantages. In this paper the piezoelectric types which has features such as; ink delivery quantity, driving control, controlling of droplet size based on color representation, generating heat and superb reliability have been introduced. By this work, we exhibit the deformation of piezoelectric elements is applied in two ways, consist of thickness deformation and sliding deformation. This chamber is included in a small slot that is created through two piezoelectric crystal plates .In addition the voltages inserted to the piezoelectric walls on both sides cause deformation mode. Due to this operation shear mode deformation occurs to both walls and via the ink pressure chamber, ink drops are delivered. Several inks applied as a dielectric material layers for conductive track in electrochemical sensors. Thus, passivation of printed sensors and deposition of adhesives can be achieved simultaneously. In this work, the presented method for the printing of UV-curable adhesive and dielectric inks demonstrates a rapid facile prototyping process.

The Flow Structure in the Narrow Gaps of Compound Channels: The Basic Flow

In the present work, a methodology for the basic flow solution in complex form channels is presented. This methodology, which could be applied to any compound channel, implements an innovative and original solution strategy which solves in a simple way the apparent nonlinearity of the problem. The solution is computed using the finite element method. As an illustration, the methodology was applied to study flows in complex channels consisting of two rectangular channels connected through a rectangular slot. The effects of the slot position (placed either at the bottom or in the centre of the channels) and height on the velocity and wall shear stress distributions and overall friction were investigated. For small slot relative heights, the flow is essentially organized as parallel channel flows with almost no interaction between them and the overall channel friction factor is insensitive to the slot position. For larger gaps, the position of the slot becomes a determinant parameter. The presence of the slot and its relative height influence the entire flow distributions and the overall friction factor. The velocity profiles in the middle of the gap were studied, and their implications on the possibility of the development of hydrodynamic instabilities were considered.

Evaluation of the impact of divertor closure on high-Z material transport and leakage in small angle slot divertor with toroidal tungsten rings in DIII-D

Predictive modeling of the closed Small Angle Slot (SAS) divertor with toroidal tungsten (W) rings in different poloidal locations is conducted to evaluate the impact of divertor closure on high-Z impurity sourcing and transport. These simulations utilize the DIVIMP code for W erosion, transport and deposition/redeposition, with background plasma solutions provided by SOLPS5.1. It is found that the level of W leakage is mostly determined by the divertor plasma conditions, the location of the W source and redeposition processes. High density plasmas in the SAS slot result in shorter ionization mean free paths than in the far-target region, resulting in higher redeposition rate. The induced friction force dominates in the near-target region, driving W impurities downstream towards the target surface. As a result, a W source at the strike point in the SAS divertor demonstrates lower net erosion and divertor leakage, despite higher gross erosion, compared to W sources in the far-target region.

Study the Effect of Combination of Shoe Height and Slot Opening width to Reduce Cogging Torque in Permanent Magnet Generator

Cogging torque is one important problem in a permanent magnet generator. With a good understanding of the phenomenon, the cogging torque can be minimized by using the multi-objective technique. This paper presents a combination technique for cogging torque reduction by an appropriate small stator slot opening width, stator shoe height with fractional technique in Permanent Magnet Generator. Cogging torque waveforms, along with other relevant characteristics are investigated in this research and by analysis using the finite element method, the combination width shoe height and magnet edge slotting effect to decline the cogging torque peak value. A significant value of cogging torque, when slot opening width of 1.55 mm and shoe height of 2.3 mm, provide the peak value of cogging torque in the structure is 0.00062 N-m for positive value and about -0.00064 N-m for the negative value. It can be concluded that this type of slot opening width of 1.55 mm and shoe height of 2.3 mm is the best structure of the fractional 8 slot, because it has any significant low of cogging torque and least of unbalance magnetic pull

The presence of the “locking effect” when the fluid flows through the cylindrical throttle channels

A study was made for the continuous flow of the working fluid through a cylindrical throttle channel (so-called “locking effect”). The flow of the fluid into the atmosphere and the change in absolute pressure at the inlet to the throttle channel ranging between 0.221 MPa and 0.24 MPa are studied. It was found that the pressure in the compressed section inside the throttle channel remains almost constant and equal to 4 kPa. A comparison is made of the experimental values of the flow rate determined for the same absolute pressure difference Δp in the separated and unseparated flow regimes. Knowing that the value of the flow coefficient μ in the zone of the existence of the “locking effect” can be determined from known data for the process of fluid outflow from holes with a sharp edge in a thin wall. Also, similar phenomena occur when fluid flows through small holes and slots in the guide, control and regulatory equipment of various hydraulic systems.

A numerical study of dynamics in thin hopper flow and granular jet**Project supported by the National Natural Science Foundation of China (Grant Nos. 11705256 and 11905272), the National Postdoctoral Program for Innovative Talents, China (Grant No. BX201700258), Young Scholar of CAS "Light of West China" Program for Guanghui Yang (Grant No. 2018-98), and the Strategic Priority Research Program of the

The dynamics of granular material discharging from a cuboid but thin hopper, including the hopper flow and granular jet, are investigated via discrete element method (DEM) simulations. The slot width is varied to study its influence on the flow. It is found the flow in the cuboid hopper has similarity with the flow in two-dimensional (2D) hopper. When the slot width is large, the flowrate is higher than the predicted value from Beverloo’s law and the velocity distribution is not Gaussian-like. For granular jet, there is a transition with varying slot width. For large slot width, there is a dense core in the jet and the variations of velocities and density are relatively small. Finally, the availability of continuum model is assessed and the results show that the performance with large slot width is better than that with small slot width.

Triple Band Antenna For WLAN/WiMAX Applications

This paper presents a compact triple band antenna for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) application. The proposed antenna has a rectangular patch with rectangular ring slot and a small rectangular shape slot in a partial ground plane. The dimensions of the patch, the ground and the two slots are optimized to obtain resonance at 1.6 GHz, 2.4 GHz and 5.2GHz frequencies

A NOVEL SMALL SIZE CPW-FED SLOT ANTENNA WITH CIRCULAR POLARIZATION FOR 5G APPLICATION

A NOVEL SMALL SIZE CPW-FED SLOT ANTENNA WITH CIRCULAR POLARIZATION FOR 5G APPLICATION

Development of Surface Eroding Thermocouples in Small Angle Slot Divertor in DIII-D

The surface eroding thermocouple (SETC) has proved to be a useful fast local temperature and heat flux diagnostic since its application in DIII-D. The SETC system in DIII-D was upgraded, and seven new SETCs were installed in the small angle slot (SAS) divertor to create a localized poloidal array to provide heat flux profiles with sub-10-ms temporal resolution. In addition, a smaller SETC was developed to increase the spatial resolution and simplify installation in the SAS divertor. The SETC-containing tiles were re-engineered with a double-wide format so that the distance between the SETCs and the tile edges is extended to 10 cm on both sides, giving additional tolerance for tile-to-tile misalignments. Mineral insulated thermocouple cable with a metal sheath has also been implemented to further reduce noise and magnetic pickup. Recent measurements obtained from the SETCs indicate that the newly installed SETC array in the SAS divertor is able to provide important heat flux information to various physics experiments in closed divertors.

Antenna performance improvement by utilizing a small parasitic slot in stacked PCBs for IoT devices

ABSTRACTThis paper proposes a simple and efficient technique to improve the antenna radiation performance in stacked printed circuit boards (PCBs) for Internet-of-Things (IoT) applications. In the proposed design, a planner loop-type ground radiation antenna with compact size is implemented at the upper PCB for 2.4 GHz applications, while the lower PCB overlaps with the upper PCB, inducing out-of-phase current distributions over the lower PCB, thereby resulting in a narrow bandwidth and low efficiency. Therefore, a small parasitic resonator is utilized on the lower PCB to diminish the undesired out-of-phase current. Higher efficiency and wider bandwidth are thus achieved by tuning the impedance characteristic of the parasitic slot, indicating the proposed technique is effective in improving antenna performance for devices with stacked PCBs.

A Compact Semi-Circular and Arc-Shaped Slot Antenna for Heterogeneous RF Front-Ends

In this paper, a new miniaturized compact dual-band microstrip slot antenna is presented. To achieve the dual-band characteristics, two adjunct partial arc-shaped small slots are joined to two main circular slots embedded in the ground of the antenna structure. With a reduced size of 30 × 28.5 × 0.8 mm3, the proposed antenna presents a dual-band characteristic. The design is optimized using a High Frequency Structure Simulator (HFSS) followed by experimental verifications. An impedance bandwidth, for S11≤10 dB, that covers the 1.8 GHz and 2.4 GHz bands is accomplished, which makes the proposed antenna basically suitable for hand-held devices and medical applications. More applications such as digital communication system (DCS) 1.71–1.88 GHz, personal communication services (PCS) 1.85–1.99 GHz, Universal and mobile telecommunications system UMTS 1.92–2.17 GHz, Bluetooth 2.4–2.5 GHz, and Wi-Fi 2.4–2.454 GHz, Industrial Scientific and Medical radio frequency (RF) band ISM-2.4 GHz, Wireless Local Area Network (WLAN-2.4)are possible by simply changing one of the geometrical antenna dimensions. The antenna is characterized by stable radiation patterns as well.