Layer Switch Research Articles

Time structures of proton pencil beam scanning delivery on a microsecond scale measured with a pixelated semiconductor detector Timepix3.

The time structures of proton spot delivery in proton pencil beam scanning (PBS) radiation therapy are essential in many clinical applications. This study aims to characterize the time structures of proton PBS delivered by both synchrotron and synchrocyclotron accelerators using a non-invasive technique based on scattered particle tracking. A pixelated semiconductor detector, AdvaPIX-Timepix3, with a temporal resolution of 1.56ns, was employed to measure time of arrival of secondary particles generated by a proton beam. The detector was placed laterally to the high-flux area of the beam in order to allow for single particle detection and not interfere with the treatment. The detector recorded counts of radiation events, their deposited energy and the timestamp associated with the single events. Individual recorded events and their temporal characteristics were used to analyze beam time structures, including energy layer switch time, magnet switch time, spot switch time, and the scanning speeds in the x and y directions. All the measurements were repeated 30 times on three dates, reducing statistical uncertainty. The uncertainty of the measured energy layer switch times, magnet switch time, and the spot switch time were all within 1% of average values. The scanning speeds uncertainties were within 1.5% and are more precise than previously reported results. The measurements also revealed continuous sub-milliseconds proton spills at a low dose rate for the synchrotron accelerator and radiofrequency pulses at 7µs and 1ms repetition time for the synchrocyclotron accelerator. The AdvaPIX-Timepix3 detector can be used to directly measure and monitor time structures on microseconds scale of the PBS proton beam delivery. This method yielded results with high precision and is completely independent of the machine log files.

Fundamentals and Applications of Network Engineering: A Comprehensive Introduction to Layer-2 Switching and Layer-3 Routing

Fundamentals and Applications of Network Engineering: A Comprehensive Introduction to Layer-2 Switching and Layer-3 Routing

Comprehensive Network Architectures: Bridging Layer-2 Switching, Layer-3 Routing, and Emerging Digital Systems

Comprehensive Network Architectures: Bridging Layer-2 Switching, Layer-3 Routing, and Emerging Digital Systems

Effect of the charge rate on the mechanical response of composite graphite electrodes: in situ experiment and mathematical analysis.

The cycling lifespan and coulombic efficiency of lithium-ion batteries are crucial to high C-rate applications. The Li-ion concentration is crucial in determining the mechanical integrity and structural stability of electrodes. In this work, graphite is selected as the working electrode due to its widespread use in the electric vehicle industry. The experimental data have shown that the electrodes with a mass loading of 6.54 mg cm-2 exhibited poor cycling performance and high charge transfer resistance at high charge rates. To explain this phenomenon, an in situ stress measurement system and a C-rate-dependent stress model are established to study the mechanical properties of the composite graphite electrode during the electrochemical process at various C-rates. Moreover, the effect of the Li-ion concentration-dependent modulus and C-rate-dependent partial molar volume is taken into account in the mathematical model. The computational curvature data fit well with the corresponding experimental data, highlighting the importance of considering lithium-ion concentration in mechanical stress. It has been found that stresses along the thickness of the active layer switch between compressive and tensile stresses due to the competition between bending stress and diffusion-induced stress. The stress at the outer surface of the composite graphite electrodes reaches a maximum magnitude of 27.5 MPa at a 1.5C-rate. In contrast, the stress at the interface of the active layer is maximum at a 0.5C-rate due to the existence of more lithium ions. Our study provides a direct insight into the quantitative analysis of electrode stresses at different C-rates.

Research on a Field Prompt Device for Substation Switch Remote Control Based on Station Control Layer Switch

The switch in the substation is operated by remote control. To prevent the on-site personnel from being injured by the explosion of the fault switch, a prompt signal shall be sent to the on-site personnel to remind them to stay away from the operating equipment before the remote operation of the primary equipment is required from the perspective of safety. At present, the method of telephone notification or no notification is adopted, which is low in efficiency and poor in operability, and it is difficult to timely and effectively notify on-site personnel. The on-site prompt device for remote switch operation can send prompt signals to on-site personnel before remote switch operation without increasing any workload by monitoring the message of the station control layer switch, which can prevent personal injury and death caused by the explosion of remote switch operation and is of great significance to safety production.

Investigation of the impact of machine operating parameters on beam delivery time and its correlation with treatment plan characteristics for synchrotron-based proton pencil beam spot scanning system.

To investigate the beam delivery time (BDT) reduction due to the improvement of machine parameters for Hitachi synchrotron-based proton PBS system. BDTs for representative treatment plans were calculated to quantitatively estimate the BDT improvement from our 2015 system at Mayo Clinic in Arizona to our system to be implemented in 2025 at Mayo Clinic in Florida, and to a hypothetical future system. To specifically assess how each incremental improvement in the operating parameters reduced the total BDT, for each plan, we simulated the BDT 10,368 times with various settings of the nine different operating parameters. The effect of each operating parameter on BDT reduction and its correlation with treatment plan characteristics were analyzed. The optimal number of multiple energy extraction (MEE) layers per spill for different systems was also investigated. The median (range) decrease in BDT was 60% (56%-70%) from the 2015 to the 2025 system. The following incremental improvement in parameters of the 2015 system for the 2025 system played an important role in this decreased BDT: beam intensity (8 to 20 MU/s), recapture efficiency (50% to 80%), number of MEE layers per spill (4 to 8), scanning magnet preparation and verification time (1.9 to 0.95 msec), and MEE layer switch time (200 to 100 msec). Reducing the total spill change time and scanning magnet preparation and verification time from those of the 2025 system further reduced BDT in the hypothetical future system. 8 MEE layers per spill is optimal for a system with 50% recapture efficiency; 16 MEE layers per spill is optimal for a system with 80% recapture efficiency; and more than 16 MEE layers per spill is beneficial only for a system close to 100% recapture efficiency. We systematically studied the effect of each machine operating parameter on the reduction in total BDT and its correlation with treatment plan characteristics. Our findings will aid new and existing synchrotron-based proton beam therapy centers to make balanced decisions on BDT benefits vs. costs when considering machine upgrade or new system selection.

A Secure Link-Layer Connectivity Platform for Multi-Site NFV Services

Network Functions Virtualization (NFV) is a key technology for network automation and has been instrumental to materialize the disruptive view of 5G and beyond mobile networks. In particular, 5G embraces NFV to support the automated and agile provision of telecommunication and vertical services as a composition of versatile virtualized components, referred to as Virtual Network Functions (VNFs). It provides a high degree of flexibility in placing these components on distributed NFV infrastructures (e.g., at the network edge, close to end users). Still, this flexibility creates new challenges in terms of VNF connectivity. To address these challenges, we introduce a novel secure link-layer connectivity platform, L2S. Our solution can automatically be deployed and configured as a regular multi-site NFV service, providing the abstraction of a layer-2 switch that offers link-layer connectivity to VNFs deployed on remote NFV sites. Inter-site communications are effectively protected using existing security solutions and protocols, such as IP security (IPsec). We have developed a functional prototype of L2S using open-source software technologies. Our evaluation results indicate that this prototype can perform IP tunneling and cryptographic operations at Gb/s data rates. Finally, we have validated L2S using a multi-site NFV ecosystem at the Telefonica Open Network Innovation Centre (5TONIC), using our solution to support a multicast-based IP television service.

Proton linac-based therapy facility for ultra-high dose rate (FLASH) treatment

As an advanced treatment method in the past five years, ultra-high dose rate (FLASH) radiotherapy as a breakthrough and milestone in radiotherapy development has been verified to be much less harmful to healthy tissues in different experiments. FLASH treatments require an instantaneous dose rate as high as hundreds of grays per second to complete the treatment in less than 100 ms. Current proton therapy facilities with the spread-out of the Bragg peak formed by different energy layers, to our knowledge, cannot easily achieve an adequate dose rate for FLASH treatments because the energy layer switch or gantry rotation of current facilities requires a few seconds, which is relatively long. A new design for a therapy facility based on a proton linear accelerator (linac) for FLASH treatment is proposed herein. It is designed under two criteria: no mechanical motion and no magnetic field variation. The new therapy facility can achieve an ultra-high dose rate of up to 300 Gy/s; however, it delivers an instantaneous dose of 30 Gy within 100 ms to complete a typical FLASH treatment. The design includes a compact proton linac with permanent magnets, a fast beam kicker in both azimuth and elevation angles, a fixed gantry with a static superconducting coil to steer proton bunches with all energy, a fast beam scanner using radio-frequency (RF) deflectors, and a fast low-level RF system. All relevant principles and conceptual proposals are presented herein.

A Hybrid SDN Switch Based on Standard P4 Code

This letter presents an enhanced hybrid Software-Defined Networking (SDN) layer-2 switch whose behavior is specified by the Programming Protocol-independent Packet Processors (P4) language. Its SDN capabilities are enabled by using P4Runtime as control plane protocol to specify the forwarding rules used by its programmable data plane. Additionally, the device is also able to exploit P4 registers for an autonomous self-definition of its forwarding capabilities, with the goal of avoiding an overload of the SDN control plane. Its performance is better than other P4 proposals based on non-standard externs and similar to other platform-dependent implementations.

Towards next generation “smart” tandem catalysts with sandwiched mussel-inspired layer switch

In this paper, we prepared a novel reactor with switchable ability to address present challenges in tandem catalyst. By introducing mussel-inspired moiety, this goal was achieved via preparing a “smart” polymer reactor which can open or closes the entry tunnel of the targeted substrate in cascade reactions. The catalyst consisted of two functional layers acting as tandem catalytic parts and one smart layer with mussel-inspired moieties as a controlled middle switch. The top and the bottom layer were made of molecularly imprinted polymers and catalytic components, like acidic parts and metal nanoparticles, respectively. The middle layer made of polymeric dopamine (PDPA) and acrylamide with self-healing ability will allow or inhibit the intermediate product for the reaction, thus controlling the process of the tandem catalysis. As a result, the novel catalyst exhibited self-controlled tandem catalysis, which provides new opportunities to design smart tandem catalysts, showing a promising prospect in this area.

Comparative Analysis of Parameter Extractor for Low-Power Precomputation Based Content Addressable Memory

Content Addressable Memory (CAM) is used in high speed searching applications and also in data compression. Recently in the network computing era, fast lookup tables are required for address resolution in network switches and routers such as LAN bridges/switches, ATM switches, and layer-3 switches. High search speed is obtained by parallel comparison. But power consumption is high in case of parallel comparison. In precomputation based CAM (PB-CAM) the comparison operation is divided into two stages to reduce the massive comparison operations in data searches. Precomputation is the way of comparing the extracted parameter from the input data in the first stage. The second stage comparison is done between the matched output of the first stage and the input data. In this paper, a Remainder Function parameter extractor is proposed as a precomputation technique to enhance the performance of low power PB-CAM. The experimental results obtained using 90 nm CMOS technology in the Cadence virtuoso show that the proposed approach achieves an average of 91% in power reduction.

P4VBox: Enabling P4-Based Switch Virtualization

Virtualization has become the powerhouse for several networking concepts, from local area networks (VLANs) to software switches, software-defined control plane, etc. Recent proposals like HyPer4, HyperVDP, and P4Visor brought the concept to the forwarding plane, by enabling emulation of several network contexts and/or composing several functions through a single program. In spite of the progress achieved, the real power of forwarding plane virtualization remains untapped. In this letter, we present P4VBox, a reconfigurable architecture for data plane virtualization. P4VBox provides parallel execution and hot-swapping of virtual switch instances, without requiring switch source code (for either emulation or program composition). We experimented P4VBox on a NetFPGA-SUME board with three virtual switches: a layer-2 switch, a simple router, and a firewall. Area occupation measurements evidence the feasibility of running up to 13 virtual switches in parallel. Compared to existing work, performance data show an improvement of up to two orders of magnitude for bandwidth and six orders for latency.

Improving dosimetric outcome for hippocampus and cochlea sparing whole brain radiotherapy using spot-scanning proton arc therapy

SummaryThis feasibility study shows that Spot-scanning Proton Arc therapy (SPArc) is able to significantly reduce the dose to the hippocampus and cochlea compared to both Volumetric Modulated Arc Photon Therapy (VMAT) and the robust optimized Intensity Modulated Proton Therapy (ro-IMPT) plans in whole brain radiotherapy. Furthermore, SPArc not only improves plan robustness but could potentially deliver a treatment as efficient as ro-IMPT when proton system’s energy layer switch time is less than 1 s.

A Future Mobile Packet Core Network Based on Ip-In-Ip Protocol

The current Evolved Packet Core (EPC) 4th generation (4G) mobile network architecture features complicated control plane protocols and requires expensive equipment. Data delivery in the mobile packet core is performed based on a centralized mobility anchor between eNode B (eNB) elements and the network gateways. The mobility anchor is performed based on General Packet Radio Service tunnelling protocol (GTP), which has numerous drawbacks, including high tunnelling overhead and suboptimal routing between mobile devices on the same network. To address these challenges, here we describe new mobile core architecture for future mobile networks. The proposed scheme is based on IP encapsulated within IP (IP-in-IP) for mobility management and data delivery. In this scheme, the core network functions via layer 3 switching (L3S), and data delivery is implemented based on IP-in-IP routing, thus eliminating the GTP tunnelling protocol. For handover between eNB elements located near to one another, we propose the creation of a tunnel that maintains data delivery to mobile devices until the new eNB element updates the route with the gateway, which prevents data packet loss during handover. For this, we propose Generic Routing Encapsulation (GRE) tunnelling protocol. We describe the results of numerical analyses and simulation results showing that the proposed network core architecture provides superior performance compared with the current 4G architecture in terms of handover delay, tunnelling overhead and total transmission delay.

An Easy In-Service Optical IP Network System for Residential Complex, Employing 1550 nm-Band CWDM and Layer-3 Switch

Abstract We have proposed and demonstrated a novel architecture to implement in Coarse Wavelength-Division-Multiplexing (CWDM) technologies to give integrated broadband services for residential complex use system. For keeping the speed of 1000 Mbps at the bus IFs, CWDM technology is employed, and eight wavelengths are allocated to eight bus IFs, respectively. We also have evaluated characteristics of the transmission by calculated and measured the throughputs. The optical IP network can be easy in-service by adjusting the number of wavelengths and optical transceivers. We believe this novel scheme can be applied for future broadband network.

Per-Flow Throughput Fairness in Ring Aggregation Network with Multiple Edge Routers

Ring aggregation networks are often employed by network carriers because of their efficiency and high fault tolerance. A fairness scheme is required in ring aggregation to achieve per-flow throughput fairness and bufferbloat avoidance, because frames are forwarded along multiple ring nodes. N Rate N + 1 Color Marking (NRN + 1CM) was proposed to achieve fairness in ring aggregation networks consisting of Layer-2 Switches (SWs). With NRN + 1CM, frames are selectively discarded based on color and the frame-dropping threshold. To avoid the accumulation of a queuing delay, frames are discarded at upstream nodes in advance through the notification process for the frame-dropping threshold. However, in the previous works, NRN + 1CM was assumed to be employed in a logical daisy chain topology linked to one Edge Router (ER). The currently available threshold notification process of NRN + 1CM cannot be employed for ring networks with multiple ERs. Therefore, this paper proposes a method for applying NRN + 1CM to a ring aggregation network with multiple ERs. With the proposed algorithm, an SW dynamically selects the dropping threshold to send in order to avoid excess frame discarding. The performance of the proposed scheme was confirmed through computer simulations.

Gigabit Security Switches Deployment - A Review

With the increasing users and services over the Internet, people demand faster data fetching and more reliable network services. However, the increasing network services and equipment causes the network management much more difficult. This is largely due to the increased size of networks and the requirement for increasingly faster and more efficient networks. In this paper, we discuss high available (HA) architecture for cost effective security switches. Security switch contains of a security switch engine (SSE) and a traditional layer-2 switch. They examine the packet content. These two components connected through a Gigabit Ethernet link. In this paper, we also discuss the types of switches. However, the majority of network administrators currently deploying gigabit networks will find that they are seeing far less than a full 100 Mbps of traffic moving over the wire. Even a standard PC with an off-the-shelf gigabit network card will be able to cope quite easily.

First demonstration of commodity L2 switch‐based passive optical network

The ‘commoditisation’ (i.e. using commodity hardware or commodity device as a hardware platform for network equipment) and ‘softwarisation’ (i.e. implementing the network function of the target equipment by software) have recently become big trends among communication carriers struggling to balance cost-efficiency and service flexibility. Especially in optical access networks, the concept of the commodity layer 2 (L2) switch-based passive optical network (PON) is attracting attention, but performance demonstrations have not been reported. This Letter offers the first performance demonstration of the L2 switch-based gigabit ethernet PON prototype constructed with an L2 switch and software-based PON-specific functions. The prototype achieves nearly 1 Gbps throughput in one-way transmission. Moreover, an additional numerical analysis confirms that the authors proposed architecture can accommodate sufficient PON port number.

Technical Note: Using experimentally determined proton spot scanning timing parameters to accurately model beam delivery time.

To accurately model the beam delivery time (BDT) for a synchrotron-based proton spot scanning system using experimentally determined beam parameters. A model to simulate the proton spot delivery sequences was constructed, and BDT was calculated by summing times for layer switch, spot switch, and spot delivery. Test plans were designed to isolate and quantify the relevant beam parameters in the operation cycle of the proton beam therapy delivery system. These parameters included the layer switch time, magnet preparation and verification time, average beam scanning speeds in x- and y-directions, proton spill rate, and maximum charge and maximum extraction time for each spill. The experimentally determined parameters, as well as the nominal values initially provided by the vendor, served as inputs to the model to predict BDTs for 602 clinical proton beam deliveries. The calculated BDTs (TBDT ) were compared with the BDTs recorded in the treatment delivery log files (TLog ): ∆t = TLog -TBDT . The experimentally determined average layer switch time for all 97 energies was 1.91 s (ranging from 1.9 to 2.0 s for beam energies from 71.3 to 228.8 MeV), average magnet preparation and verification time was 1.93 ms, the average scanning speeds were 5.9 m/s in x-direction and 19.3 m/s in y-direction, the proton spill rate was 8.7 MU/s, and the maximum proton charge available for one acceleration is 2.0 ± 0.4 nC. Some of the measured parameters differed from the nominal values provided by the vendor. The calculated BDTs using experimentally determined parameters matched the recorded BDTs of 602 beam deliveries (∆t = -0.49 ± 1.44 s), which were significantly more accurate than BDTs calculated using nominal timing parameters (∆t = -7.48 ± 6.97 s). An accurate model for BDT prediction was achieved by using the experimentally determined proton beam therapy delivery parameters, which may be useful in modeling the interplay effect and patient throughput. The model may provide guidance on how to effectively reduce BDT and may be used to identifying deteriorating machine performance.

Online Measurement-Based Adaptive Scalable Video Transmission in Energy Harvesting Aided Wireless Systems

We consider the point-to-point adaptive transmission of scalable video coding streams over a fading channel in energy harvesting (EH) aided communication systems, where the transmitter is equipped with an EH device and a rechargeable battery. The aim of this paper is to enable the transmitter having the ability of adaptively adjusting the number of video layers to be transmitted according to the available energy. Since the depletion of the energy in the battery acts as a trigger for the interruption of the video transmission, we define the energy starvation probability for equivalently characterizing a quality-of-experience (QoE) metric. We formulate the problem of EH-aided video transmission as a constrained optimization problem, maximizing the number of video layers for transmission while keeping the energy starvation probability below a threshold. Classic large deviation theory is invoked for estimating the energy starvation probability from online measurements. Consequently, our dynamic layer switch algorithm operates with no prior statistical knowledge of both the EH process and of the channel quality. Furthermore, the technique of perturbation analysis that constructs a perturbed sample path from an original sample path is invoked for improving the performance of the proposed method. Our experimental results verify that the algorithms proposed have the adaptation capability to accommodate both the energy-dynamics and the channel-dynamics for improving the video quality subject to an unobjectionable level of transmission interruption rate.