Short Slot Research Articles

Theoretical Design and Numerical Simulation of Beam-Wave Interaction for <inline-formula> <tex-math notation="LaTeX">$G$ </tex-math> </inline-formula>-Band Unequal-Length Slots EIK With Rectangular Electron Beam

A beam-wave interaction model for G-band rectangular beam extended-interaction klystron (EIK) with unequal-length slots is proposed and analyzed to achieve high output power and broad bandwidth. The length ratio of long slot with short slot is carefully optimized to obtain a large effective characteristic impedance and wide mode separation. The influence of beam tunnel size on the effective characteristic impedance is studied with the beam aspect ratio of 2.3:1. The beam conductance for 5-gap, 7-gap, and 11-gap cavities are analyzed theoretically to optimize the beam-wave interaction stability. Furthermore, beam current and input power are investigated to obtain high performance. The analysis of fabrication tolerance and alignment tolerance indicates that less than 5- $\mu \text{m}$ machining precision is required. With beam current of 0.40 A and voltage of 16.5 kV, 3-D PIC simulation predicts peak power of 1139 W and 3-dB bandwidth of 1.15 GHz, with efficiency of 17.3% and gain of 37.5 dB. In addition, PIC simulations are compared with 1-D AJDISK calculations, the approximate results with similar tendencies indicate that our proposed beam-wave interaction model for G-band EIK is relatively reliable.

Appointment overbooking with different time slot structures

Unattended appointments result in underperformance of a healthcare service provider. Such uncertainty in the appointment process not only lowers healthcare utilization and productivity but also hinders patients from having timely access to healthcare services and extends waiting time for receiving medical examinations or treatments. In this study, we formulate this stochastic optimization problem for appointment scheduling as its two-stage deterministic equivalent to simultaneously optimize overbooking and scheduling decisions to compensate patient no-shows with different time slot structures. We examine the impacts of three types of time slot structures, which are of fixed-length slot intervals, dome-pattern slot intervals and flexible appointment start times, on the efficiency of the system. With the optimal solutions found, we investigate the interaction between the time slot structure and the optimal overbooking solution. We found that the flexibility in appointment start times result in a “dome-dome-dome pattern with alternate long and short time slots” and could achieve a better patient experience (regarding the patient waiting time) while maintaining the same service provider efficiency (regarding the resource overtime and idle time), compared with the pre-defined time intervals. While there has been a large body of literature on appointment scheduling, to the best of our knowledge, this “dome-dome-dome” pattern has not been reported in the existing literature. Sensitivity analysis further shows that the flexible slot scheme is more effective when the number of overbooked patients is relatively low and the service duration is relatively long.

A Dual-Channel Acquisition Method Based on Extended Replica Folding Algorithm for Long Pseudo-Noise Code in Inter-Satellite Links.

Inter-satellite links are an important component of the new generation of satellite navigation systems, characterized by low signal-to-noise ratio (SNR), complex electromagnetic interference and the short time slot of each satellite, which brings difficulties to the acquisition stage. The inter-satellite link in both Global Positioning System (GPS) and BeiDou Navigation Satellite System (BDS) adopt the long code spread spectrum system. However, long code acquisition is a difficult and time-consuming task due to the long code period. Traditional folding methods such as extended replica folding acquisition search technique (XFAST) and direct average are largely restricted because of code Doppler and additional SNR loss caused by replica folding. The dual folding method (DF-XFAST) and dual-channel method have been proposed to achieve long code acquisition in low SNR and high dynamic situations, respectively, but the former is easily affected by code Doppler and the latter is not fast enough. Considering the environment of inter-satellite links and the problems of existing algorithms, this paper proposes a new long code acquisition algorithm named dual-channel acquisition method based on the extended replica folding algorithm (DC-XFAST). This method employs dual channels for verification. Each channel contains an incoming signal block. Local code samples are folded and zero-padded to the length of the incoming signal block. After a circular FFT operation, the correlation results contain two peaks of the same magnitude and specified relative position. The detection process is eased through finding the two largest values. The verification takes all the full and partial peaks into account. Numerical results reveal that the DC-XFAST method can improve acquisition performance while acquisition speed is guaranteed. The method has a significantly higher acquisition probability than folding methods XFAST and DF-XFAST. Moreover, with the advantage of higher detection probability and lower false alarm probability, it has a lower mean acquisition time than traditional XFAST, DF-XFAST and zero-padding.

Design of remote handling, nuclear and vacuum compatible connectors for mineral insulated thermocouples of ITER neutral beam injectors

Mineral insulated (MI) thermocouples will be connected to MI extension cables through custom connectors for sensors positioned on in-vessel components of the ITER neutral beam injectors.The connectors can house up to 64 metal-ceramic terminations of MI thermocouples locked in position by insulating plates and bushes; an external shielding shell will be mounted as protection. Coupling between shields and insulating plates have been developed with shadow edges to avoid deposition of conductive coatings of sputtered materials, so preserving the electrical insulation.Electrical design has been developed to shield signals from electromagnetic interference and to isolate the sensor shield from the vessel grounding, so avoiding ground loops.Remote handling design incorporates a long ball-ended dowel that locates in a circular hole and short parallel dowels that locate in a short slot to provide high level of position control within a compact arrangement. The plug has been provided with two grips for the manipulator interface.Mechanical design has been accomplished by selecting materials and solutions compatible with vacuum and radiation resistance in the ITER environment, considering the manufacturing feasibility especially for machinable glass-ceramic used for plates and bushes, verifying the mating alignment of standard contact pins also at the signal feedthrough interface.

Four‐feed reconfigurable MIMO antenna for metal‐frame smartphone applications

A reconfigurable multiple-input multiple-output (MIMO) antenna design for the smartphone with a metal frame capable of covering hepta-band LTE/WWAN is proposed. The proposed antenna has four monopole slots (two long slots and two short slots) etched on the top and bottom side of the system ground, respectively. Two PIN diodes are inserted into the two long monopole slots. When these two PIN diodes are OFF, the two long monopole slots can generate the desired lower-band (824-960 MHz) which can be applied in a 2 × 2 MIMO system. When these two PIN diodes are ON, the corresponding lengths of these two long slots are decreased to the same length as the short slots. Then these four ports can excite the desired upper-band (1710-2690 MHz) which can be used for a 4 × 4 MIMO system. In addition, the performances of the proposed antenna including the return loss, isolation, efficiency, envelop correlation coefficient, mean effective gain, and channel capacity are presented.

A wideband compact horizontally polarized omnidirectional antenna for 2G/3G/LTE

A compact horizontally polarized omnidirectional slot antenna with a wide working band is presented in this article. The proposed antenna consists of 4 shorter driven cross-shaped slots, 4 longer parasitic cross-shaped slots, and a feeding network. Four shorter slots, placed on the same side of a circular substrate, are fed by a feeding network printed on the other side with uniform phase and magnitude. To enhance the bandwidth of the antenna, 4 longer cross-shaped slots are inserted between adjacent longer slots to produce an additional resonant frequency. All 8 slot radiators placed symmetrically along the circumference results in an omnidirectional horizontal polarized radiation pattern. By utilizing cross-shaped slots, a compact size of 0.53λL × 0.53λL × 0.005λL (λL is the free space wavelength at the lowest operational frequency) is achieved. The prototype of the proposed antenna is fabricated and measured. The measured results reasonably agree with the simulated results. The measured working band for |S11|<–10dB is from 1.62 to 2.81 GHz which successfully covers the 1.7 to 2.7 GHz 2G/3G/LTE bands. The measured gain variation in azimuthal angle is <1.7 dB within 1.7 to 2.7 GHz, and the cross polarization level is <–27 dB in the horizontal plane.

Feasibility of Using a Novel 2.45 GHz Double Short Distance Slot Coaxial Antenna for Minimally Invasive Cancer Breast Microwave Ablation Therapy: Computational Model, Phantom, and In Vivo Swine Experimentation.

Microwave ablation (MWA) by using coaxial antennas is a promising alternative for breast cancer treatment. A double short distance slot coaxial antenna as a newly optimized applicator for minimally invasive treatment of breast cancer is proposed. To validate and to analyze the feasibility of using this method in clinical treatment, a computational model, phantom, and breast swine in vivo experimentation were carried out, by using four microwave powers (50 W, 30 W, 20 W, and 10 W). The finite element method (FEM) was used to develop the computational model. Phantom experimentation was carried out in breast phantom. The in vivo experimentation was carried out in a 90 kg swine sow. Tissue damage was estimated by comparing control and treated micrographs of the porcine mammary gland samples. The coaxial slot antenna was inserted in swine breast glands by using image-guided ultrasound. In all cases, modeling, in vivo and phantom experimentation, and ablation temperatures (above 60°C) were reached. The in vivo experiments suggest that this new MWA applicator could be successfully used to eliminate precise and small areas of tissue (around 20–30 mm2). By modulating the power and time applied, it may be possible to increase/decrease the ablation area.

A Balanced Feed Filtering Antenna With Novel Coupling Structure for Low-Sidelobe Radar Applications

A fourth-order filtering patch antenna with a novel coupling structure is presented in this paper. Using the proposed coupling structure, both the balanced coupling feed and cross-coupling are realized. Two identical slots etched on the ground plane are utilized to excite the radiating patch with the reduced cross-polarization level. A short slot etched on the ground plane is employed for cross-coupling, which introduces two controllable radiation nulls with a steep roll-off rate. In addition, owing to the split-ring resonators and hairpin resonators, the improved impedance bandwidth is achieved with the fourth-order filtering response. To demonstrate the proposed design techniques, both the filtering antenna element and the low-sidelobe array are designed, fabricated, and measured. The measured results show that the proposed antenna has the impedance bandwidth of 12% (4.78–5.39 GHz) with the total height of $0.06\lambda _{0}$ , the cross-polarization level lower than −31 dB, and two radiation nulls with the suppression higher than 31 dB. For the low-sidelobe antenna array, wide impedance bandwidth is also obtained with the sidelobe level below −28.7 dB, the cross-polarization level below −34 dB, and the out-of-band suppression better than 25 dB.

A Time-Efficient Pair-Wise Collision-Resolving Protocol for Missing Tag Identification

Radio frequency identification (RFID) technology has been employed in wide-raging application domains. In most RFID applications, time-efficient identification of missing tags is one of the most fundamental objectives, especially for asset management and anti-theft purposes. In this paper, we propose a time-efficient pair-wise collision-resolving missing tag identification (PCMTI) protocol for large-scale RFID systems. In the protocol, two novel strategies, i.e., the pair-reply and two-collision slot (i.e., a slot with two exact tag responses) resolving strategies, are proposed. The pair-reply strategy can verify two tags in one short response slot simultaneously, while the two-collision slot resolving strategy further increases the number of tags verified in each frame. Both theoretical analysis and simulated results are presented to demonstrate the superiority of the proposed PCMTI protocol, which is capable of outperforming the state-of-the-art comparative protocols with at least a 30% reduction in average identification time for verifying one tag.

Coupling topology of substrate integrated waveguide filter using unequal length slots with non‐resonating nodes

A novel coupling topology of substrate integrated waveguide filter with unequal-length slots is proposed. This filter consists of two resonators and a pair of unequal-length slots, which can be considered as two-stage bypass coupling resonators. There exist two resonant modes (TE101 and TE102) in each resonator. TE101 mode is coupled by the long slot, and TE102 mode is coupled by the short slot, which can achieve two resonant modes couplings between adjacent cavities. This structure uses TE102 mode to design the centre frequency of the passband and regards TE101 mode as spurious response. As a result, this filter leads to three transmission zeros (TZs), two TZs locate above the passband and one TZ is below the passband. The filter is fabricated and measured, the measured results agree well with simulated ones.

Uncertainties in Grout Penetrability Measurements; Evaluation and Comparison of Filter pump, Penetrability Meter and Short Slot

To measure grout penetrability in fractured hard rock, various measuring instruments have been developed over the years. Penetrability meter and Filter pump have been designed to use in both the lab and the field. Short slot has been applicable mainly in the lab due to its complexity. The fact, that these instruments have been built based on different assumptions, limitations, and test conditions, makes their results occasionally in contradict. Deficiency in design of the instruments as well as the methods of evaluating grout penetrability is additionally a basis for uncertainty in results. This study is an experimental effort to determine and thoroughly perceive the nature of the most governing uncertainties in grout penetrability measurements. The test apparatus, procedure, and method used to evaluate the grout penetrability in both Penetrability meter and Filter pump were thus modified. The aim was to control the corresponding uncertainties and make their limitations and test conditions as similar as possible with the ones in Short slot. The results suggested that to obtain a more realistic evaluation of the grout penetrability, measurement should be accomplished at both the high and the low pressures with sufficient grout volume using Short slot. Moreover, application of both Filter pump and Penetrability meter is no longer recommended due to the revealed uncertainties.

Dynamic charging-while-driving systems for freight delivery services with electric vehicles: Traffic and energy modelling

This paper presents a research on traffic modelling developed for assessing traffic and energy performance of electric systems installed along roads for dynamic charging-while-driving (CWD) of fully electric vehicles (FEVs).The logic adopted by the developed traffic model is derived from a particular simulation scenario of electric charging: a freight distribution service operated using medium-sized vans. In this case, the CWD service is used to recover the state of charge of the FEV batteries to shortly start with further activities after arrival at the depot.The CWD system is assumed to be implemented in a multilane ring road with several intermediate on-ramp entrances, where the slowest lane is reserved for the dynamic charging of authorized electric vehicles. A specific traffic model is developed and implemented based on a mesoscopic approach, where energy requirements and charging opportunities affect driving and traffic behaviours. Overtaking manoeuvres as well as new entries in the CWD lane of vehicles that need to charge are modelled according to a cooperative driving system, which manages adequate time gaps between consecutive vehicles. Finally, a speed control strategy is simulated at a defined node to create an empty time-space slot in the CWD lane, by delaying the arriving vehicles. This simulated control, implemented to allow maintenance operations for CWD that may require clearing a charging zone for a short time slot, could also be applied to facilitate on-ramp merging manoeuvres.

A Differential-Fed Microstrip Patch Antenna With Bandwidth Enhancement Under Operation of TM10and TM30Modes

A differential-fed microstrip patch antenna (MPA) with bandwidth enhancement is proposed under the operation of TM10 and TM30 resonant modes in a single patch resonator. Initially, a rectangular differential-fed MPA is theoretically investigated so as to demonstrate that all of the undesired modes between the TM10 and TM30 modes are suppressed or removed out effectively. Then, by symmetrically introducing two pairs of shorting pins, the resonant frequency of TM10 mode is progressively turned up. After that, with the help of two long slots, the resonant frequency of TM30 mode is decreased with slight effect on that of TM10 mode. Furthermore, a short slot is inserted at the center of the patch to cancel the parasitic inductances of the shorting pins and probe feeds. With this arrangement, these two radiative resonant modes are moved in proximity to each other for wideband antenna. Finally, the proposed differential-fed MPA is fabricated and measured. Experimental results illustrate that the impedance bandwidth ( $\vert S_{{{\text {dd}11}}}\vert dB) of the antenna has gained a tremendous increment up to about 13% (1.88–2.14 GHz), while keeping a low profile property with the height of 0.029 free-space wavelength. Additionally, the antenna has achieved a stable gain varied from 5.8 to 7 dBi over the operating band.

Design and development of CPW fed monopole antenna at 2.45 GHz and 5.5 GHz for wireless applications

The behaviour of various families of the antenna structures is studied. In that, CPW (Coplanar Waveguide) fed antennas show better behaviour for the Wireless applications. The slot antenna is used for precise operating frequency, where the frequency spectrum is 2.45GHz and 5.5GHz. To achieve the proposed frequency, the slot antenna is fed with Coplanar waveguide is implemented and measured with dimensions of 70mm×70mm. To increase the bandwidth, first the mid section of two short slots of either side of the single pole length is increased slowly to check out the maximum bandwidth. The achieved peak bandwidth gradually starts decreasing at some length, considering the achieved peak value, The length responsible for decreasing peak value is to be noted. Now for obtaining the operating frequency lies in the frequency band, the mid section of long slot has to be decreased gradually; thus, operating frequency shows at 2.45GHz and 5.51GHz with return loss of −20dB, and the whole design is printed on the FR4 substrate for better efficiency to the proposed frequency at maximum bandwidth, and thereafter to check out the characteristics of antenna the parameters such as Return loss characteristics, VSWR, Azimuth pattern, Elevation pattern and 3D distribution pattern.

Studying the Influence of Opening Angles of Planar Short Slot Microwave Antennas on Their Electrodynamic Characteristics

We study the characteristics of planar symmetric slot antennas with linearly expanding openings, whose dimensions are comparable with a radiation wavelength of 30 mm. The radiation patterns of the antennas under consideration are calculated experimentally, measured experimentally, and analyzed for opening angles of 60°, 90°, and 120°. The influence of the antenna opening angle on the directivity of the antennas is revealed. The experimentally measured antenna radiation patterns are found to agree well with the developed mathematical models at the frequencies (10 ± 2) GHz.

We need to talk about Wittgenstein: The practice of dialogue in the classroom and in assessment

Is philosophy the pursuit of knowledge, as first year students with a dictionary sometimes write? With an aim to inspire and encourage philosophical inquiry, offering an invitation to participate in a process of discovery? Or are philosophers charged with teaching the history of such pursuits – who argued, proved, disproved what? On the first account, philosophy is a subject that resists information-transmission, and requires exploration, creativity, discussion and dialogue. On the second, teaching centres on information-transmission, etching old ideas into the minds of budding scholars, in short time slots. Though there need not be a division, there is a need to recognise where approaches differ. In this way, we can ensure sufficient time and space for the sometimes unquantifiable: imaginative, creative pursuits in philosophy, with space for independent, original thinking. This paper explores these ideas alongside approaches to teaching, and offers a paradigm for incorporating dialogue in the learning and practice of philosophy.

Time-Slot Reservation based Multiple Access Protocolfor the Internet of Things

In the Internet of Things (IoT), a gateway and a set of IoT devices (IoTDs) form a startopology and the IoTDs compete between them for sending uplink communication during short time slots. Therefore, in this paper, we propose a novel multiple access protocol with time-slot reservation that can increase the success rate of the uplink data transmission with collision avoidance in the IoT. Further, using a modem calculator tool from the LoRa Alliance, we evaluate the system performance of the low power wide area network which is designed for sensors and applications in terms of equivalent bitrate, time on air, and Tx energy consumption for the uplink of the IoTDs.

An Energy-Efficient MAC Protocol for Medical Emergency Monitoring Body Sensor Networks.

Medical emergency monitoring body sensor networks (BSNs) monitor the occurrence of medical emergencies and are helpful for the daily care of the elderly and chronically ill people. Such BSNs are characterized by rare traffic when there is no emergency occurring, high real-time and reliable requirements of emergency data and demand for a fast wake-up mechanism for waking up all nodes when an emergency happens. A beacon-enabled MAC protocol is specially designed to meet the demands of medical emergency monitoring BSNs. The rarity of traffic is exploited to improve energy efficiency. By adopting a long superframe structure to avoid unnecessary beacons and allocating most of the superframe to be inactive periods, the duty cycle is reduced to an extremely low level to save energy. Short active time slots are interposed into the superframe and shared by all of the nodes to deliver the emergency data in a low-delay and reliable way to meet the real-time and reliable requirements. The interposition slots can also be used by the coordinator to broadcast network demands to wake-up all nodes in a low-delay and energy-efficient way. Experiments display that the proposed MAC protocol works well in BSNs with low emergency data traffic.

Rotated Logging Storage Architectures for Data Centers: Models and Optimizations

We propose Ro tated Lo gging (RoLo), a new logging architecture for parallel disk-based mirrored storage systems for enhanced energy efficiency, which is one of the key concerns in modern data centers. By spreading destaging I/O activities among short idle time slots and proactively reclaiming the stale logging space, RoLo rotates loggers among a logical logging space pool formed collectively from the free storage space available among mirrored disks. We develop three flavors of RoLo, that is, RoLo-P/R/E, to emphasize performance, reliability, and energy efficiency respectively. Without the extra dedicated log disks and the corresponding centralized destaging, RoLo eliminates the additional hardware and energy costs, potential single point of failure and performance bottleneck. Furthermore, RoLo-P/R/E, applied to specific scenes correctly, can prolong the lifecycle of the disks and improve the system's energy efficiency by reducing the disk spin up/down frequency. We propose RoLo-S to further alleviate the performance bottleneck and energy consumption caused by frequent disk head seeks in on-duty logger disks. We have implemented RoLo and RoLo-S on real disk systems. Extensive trace-driven evaluations demonstrate the advantages of the three RoLo schemes over both a RAID10 system with centralized logging architecture and a typical RAID10 system, and the advantages of RoLo-S over RoLo.

Design and analysis of collaborative EPC and RAN caching for LTE mobile networks

The explosive growth of mobile video traffic brings a great pressure on LTE mobile networks. Deploying caches at the evolved packet core (EPC) and radio access network (RAN) in LTE mobile networks can efficiently relieve this pressure by reducing duplicate content transmissions. In this paper, we propose a collaborative caching framework for the LTE mobile network with caches deployed at the EPC and RAN to reduce the bandwidth cost of Internet access and improve the end-user experience in terms of delay and congestion. Based on this framework, we decompose the caching problem into a content placement subproblem and a request routing subproblem. We solve the content placement subproblem with a greedy placement algorithm by utilizing the matroid and submodular properties. As for the request routing subproblem, we solve it by transforming it into the problem of maximizing a submodular function subject to a matroid constraint and present a greedy algorithm that schedules request routing with short time slot. The proposed CollaCache scheme can achieve at least 1/2 of the optimal solution in terms of bandwidth cost saving. Experimental results show that CollaCache can save more costs and support more requests compared with other schemes.