bluuebunny/crossref_metadata_2025 huggingface dataset:
NEW SELECTIVE SORBENTS FOR THE EXTRACTION OF ALKALI METAL IONS
Authors: Kurmanaliev M.K. , Shaikhova Zh.E. , Alimkulova Zh.Dzh. , Abilkasova S.O. , Daumetova S.T.
Published: December 2024

Macromolecules with crown ether groups represent a fundamentally new type of sorbents whose active centers are ligands that retain electroneutrality during simultaneous binding of cations, anions or organic compounds. The aim of this work is to study the conditions for the preparation of polymeric sorbents containing diaminodicyclohexyl crown-ethers and to investigate the activity of these sorbents with respect to the extraction of alkali metal cations. Chemical grafting of cycloaliphatic crown ethers onto a macroporous chloromethylated copolymer of styrene and divinylbenzene was carried out. Under selected conditions, diaminodicyclohexyl-18-crown-6 produced polycrown- ethers with a content of crown-ether groups of 1.42 mmol/g, while diaminodicyclohexyl-24-crown-8 produced a content of macrocyclic groups of 1.24 mmol/g.  The recovery of alkali metals under static conditions by grafted type sorbents based on different macrocycles has been investigated. High values of distribution coefficients of alkali metals (Na+, K+, Cs+) by synthesized sorbents in acidic medium are shown. The following selectivity series were found for the sorbent with diaminodicyclohexyl-18-crown-6 fragments:  К+ ˃ Cs+ ˃ Na+, and for the sorbent with diaminodicyclohexyl-24-crown-8 fragments: Cs+ ˃ K+ ˃ Na+.  The efficiency of the obtained sorbent for the extraction of alkali metal cations was shown.
БИОЛОГИЧЕСКАЯ АКТИВНОСТЬ ПОЛИФЕНОЛЬНОГО СОЕДИНЕНИЯ РАСТЕНИЙ ВЕРБЛЮЖЬЕЙ КОЛЮЧКИ (ALHAGI KIRGISORUM S)
Authors: Смаилов С.К. , Габдуллина Е.Ж. , Лесова Ж.Т. , Асембаева Э.К. , Нурмуханбетова Д.Е.
Published: December 2024

Флаваноиды – растительные ароматические соединения, производные дифенилол-пропана (C6-C3-C6) различной степени окисления и замещения. Флавоноиды относятся к производным хромана и хромона, содержащим арильный радикал в положении 2, 3 или 4. Они обладают антиоксидантной активностью, поглощают свободные радикалы, предотвращают ишемическую болезнь сердца, обладают гепатопротекторным, противовоспалительным и противоопухолевым действием, а также потенциальной активностью против вирусов.
Целью настоящей работы было изучение биологической активности полипроантоцианидина (флавоноида из водно-этанольного экстракта растения верблюжьей колючки (Alhagi kirghisorum S.) при биосинтезе белка в модельной бесклеточной системе.
В результате проведенных исследований было показано, что полипроантоцианидин (ППА) в микромолярных концентрациях специфически и обратимо связывает эукариотический фактор инициации биосинтеза белка eIF-2 (ингибирование 2 этапа биосинтеза белка). Синтез полипептида на рибосоме (3 этап биосинтеза белка) не блокируется в присутствии ППА как в случае синтеза полипептидов на матричной РНК вируса табачной мозаики, так и в случае реакции удлинения полипептида на искусственной матрице (поли У). Реакция аминоацилирования транспортной РНК аминоацил-тРНК-синтетазами (1 этап биосинтеза белка) также не блокируется полипроантоцианидином. Ингибирование синтеза вирусного белка путем подавления активности eIF-2 в инфицированных вирусом клетках является одним из механизмов противовирусной защиты у млекопитающих.
Противовирусная активность была показана для растительных флаваноидов, таких как проантоцианидин A2, катехин и их производные. Можно сделать вывод, что специфическое взаимодействие полипроантоцианидина из растений верблюжьей колючки (Alhagi kirghisorum S.) с фактором инициации eIF-2 является частью системы противовирусной защиты растений.
Performance of Super-Twisting MPPT Control for a Standalone PV System
Authors: Messaoudi Fethi , Farhani Fethi , Zaafouri Abderrahmen
Published: December 2024

Renewable energies are the key to sustainable development. They are the seat of a winning energy strategy. In particular, photovoltaic energy (PV) is one of the most widespread of these energies. But this energy suffers from its intermittency due to changing meteorological conditions, hence the need to follow the maximum power point of this energy at each moment. This paper focuses on the sliding mode control command to optimize the maximum power search. Thus we spread the evolved command on sliding mode control noted super twisting control as an MPPT approach. This latter is used in hybrid with the conventional incremental conductance similar method to the conventional hybridization incremental conductance-sliding mode control. The evolved approach is tested under MATLAB/Simulink with two other methods, such as the incremental conductance and its hybridization with sliding mode control. The results show a considerable minimization of the phenomena of ripple and chattering, thus improving MPPT efficiency.
Study on the Robotic Arm Trajectory Compensation System with Deviation Sensing
Authors: Liu Chao-Chung , Liu Jun-Chi , Liu Chao-Shu
Published: December 2024

Robotic arms play an important role in the automation industry. Robotic arms plan processing paths based on the shape of the workpiece. However, the processing path often deviates due to inaccurate placement of the workpiece. To solve the issue of deviations, this paper develops a trajectory compensation system for a robotic arm with offset perception. This system uses the concept of workpiece boundary projection and designs an offset calculation algorithm by comparing the dimensions of the workpiece drawings, correcting errors caused by missing corners of the workpiece. In terms of operation, the system uses photoelectric sensors to quickly scan the workpiece boundary and immediately calculate the displacement and rotational offset of the workpiece. Subsequently, when deviations occur due to different placement positions of the workpiece, the robotic arm’s motion path and action must be corrected and compensated to maintain precision. Tests on selected workpieces show that the corrected rotational angle error is less than 0.4 degrees, and the translational error is less than 0.7 millimeters. Since these correction error values are lower than the 1.0 mm error threshold for the robotic arm’s trajectory tracking control. The offset-sensing robotic arm trajectory compensation system developed in this study can satisfy the requirements of smart automation production lines and arrive at the manufacturer’s application standards.
Phase Structure and Electrical Properties of Na0.5K0.5NbO3-BiFeO3 Lead-Free Piezoceramics
Authors: Chen Hong
Published: December 2024

Lead-free piezoelectric ceramics (1-x)NKN-xBiFeO3 are prepared by the standard electronic ceramics preparation process. Effects of different xBiFeO3 on sintering properties, phase structure, micro-structure and electrical properties of (1-x)NKN-xBiFeO3 ceramics are studied. The results show that the (1-x) NKN-xBiFeO3 sintered at 1150 °C have a high relative density (>90%, x=0.006, RD=98.63 %). XRD spectra show that all the samples possess pure orthorhombic perovskite structure at room temperature. SEM show that the (1-x)NKN-xBiFeO3 ceramics with x=0.006 exhibit fine grains with dense surface. Dielectric temperature spectra show that the orthogonal-tetragonal phase transition temperatures To-t and Curie temperature Tc of the ceramic sample move to the low temperature region. As x=0.006, the dielectric loss tanδ of the ceramic first increases, then decreases, and then increases rapidly with the increase of temperature. The ceramic with x=0.006 exhibit a high remanent polarization (Pr=25.90 μC/cm2) and high piezoelectric coefficient (d33=181 pC/N), exhibit a low coercive field (Ec=10.28 kV/cm), a low electromechanical coupling coefficient (kp=0.139, kt=0.138), a low mechanical quality factor (Qm=12.49) and a low dielectric loss (tanδ=0.045).
Study on Ion Aluminizing Technology of Structural Steel Based on Physical Vapor Deposition
Authors: Han Dongning , Wang Yaowei , Yang Kun , Qiu Yuan , Wang Haolei
Published: December 2024

This study investigates the potential of ion-plated aluminum technology for modern industrial applications by applying a protective coating to 20# steel and evaluates the macroscopic and microscopic morphology, thickness (8∼13μm), bonding strength, and performance of the coating in highly corrosive environments. Experimental results indicate that ion-plated aluminum technology significantly improves the surface properties of the untreated material, with the corrosion current decreasing from 10-0.77A/cm2 to 10-2.75A/cm2. Additionally, after a neutral salt spray test, the samples exhibited no white corrosion products after 96 h and resisted red rust formation for up to 360 h. This analysis demonstrates that ion-plated aluminum technology enhances the service life and reliability of materials, offering an environmentally friendly alternative to conventional metal coatings and showing significant potential for broad industrial applications.
A Hybrid Optimization Approach for Efficient Hole Drilling Path Minimization
Authors: Dhouib Souhail , Zouari Alaeddine
Published: December 2024

This paper introduces a novel hybrid optimization method combining two techniques namely the Dhouib-Matrix-TSP1 (DM-TSP1) greedy algorithm and a population-based metaheuristic the Artificial Bee Colony (ABC) in order to address the multi-hole drilling operations. The proposed approach leverages the DM-TSP1 to create different feasible solutions, which are then optimized by the ABC algorithm to generate the minimal trajectory for a tool path. Four case studies are simulated to prove the performance of the proposed technique and the generated results demonstrate that ABC-DM-TSP1 consistently outperforms standard metaheuristics like the Bat metaheuristic, the Particle Swarm Optimization method and the Ant Colony Optimization metaheuristic with improvements in path length ranging from 0.24% to 9.35%. This reduction in tool path length directly translates to lower machining times, energy consumption, and production costs. The proposed method offers a robust and efficient solution for optimizing drilling paths in manufacturing, paving the way for future exploration in other machining applications.
Position Tracking for a Series of Mass-Spring-Damper System via Decentralized Control Design
Authors: Mao Zheng-Ji
Published: December 2024

A position tracking for a series of mass-spring-damper system via decentralized control design is proposed. First we derive the dynamical model for each subsystem with interconnections. Under the constraint of the fix points of this model, the reference output to be tracked is chosen. Since this is tracking but not regulation, some constant input should be provided and calculated in advance. Then based on the optimal control technique, the decentralized control design is investigated to guarantee the global exponential stability of the overall system. Computer simulations of a 4-mass interconnected mass-spring-damper system are conducted. From these results, all the states approach their reference values exponentially. This has shown the feasibility of our decentralized control design.
Virtual Models for Operating on Mobile Devices
Authors: Wang Xiaofei , Xu Jinyou , Xue Yahong , Zhang Runfeng , Hao Tianze
Published: December 2024

In recent years, the virtual reality technique has been widely used in many fields. One of the most popular applications is for generating virtual models that can be operated on the screen. In the paper, three methods of obtaining virtual models are introduced. One method is by scanning the quick response code. Another method is the use of CADbro software. The third way is to develop an app to help the digital world emerge in real-life scenarios. With the help of virtual technology, ways of teaching, modes of production, and film production are changing. The three methods mentioned in the paper make it easy to generate virtual models for people to operate on mobile devices. Virtual models generated by the three methods can be operated by touching the screen or operating the mouse, whenever and wherever.
Detection Method for Illegally Increased Capacity of Distribution Transformers Based on DBSCAN-ELM
Authors: Xuan Lv , Sun Yifei , Wang Mengyu , Shi Xiaolin , Guo Ziqi , Yuan Changyan
Published: December 2024

The unauthorized increase in transformer capacity by users not only infringes upon the interests of power enterprises but also impacts the safe and stable operation of the power system. This paper analyzes the limitations of existing capacity detection technologies and proposes an online detection method for unauthorized capacity expansion of distribution transformers by fully leveraging the advantages of the current big data environment in the power industry. Starting from the basic balance equation of transformers, this paper derives a dimensionality reduction mapping method for transformer operational data and proposes the use of the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm for data cleaning. Furthermore, a capacity expansion calculation model is derived that uses primary voltage, secondary voltage, and secondary current as parameters to calculate primary current, and the Extreme Learning Machine (ELM) algorithm is proposed as the training algorithm for this model. Finally, experimental verification is conducted using real data. The experimental results demonstrate that the model proposed in this paper requires less training time, exhibits high detection accuracy, and enables online screening of capacity expansion behaviors.
Named Entity Recognition Study for Distribution Network Operation
Authors: Zhang Peng , Yang Zhiling , Dong Xinghui , Li Jia , Chen Senye
Published: December 2024

With the development of smart grid technology, how to effectively deal with the large amount of text information generated in the process of distribution grid operation is particularly important. Named entity recognition is a key technology to construct knowledge graph of distribution grid operation, but there are problems such as difficulty in entity recognition and low accuracy. In response to the appealing situation, this paper proposes a named entity recognition model based on the fine-tuning of RoBERTa-wwm pre-trained language model, and through the comparative experimental analysis, the model in this paper reaches 94.68% of the F1 value on the distribution network operation dataset, which is more advantageous than the existing model. On this basis, the knowledge graph of distribution network operation is constructed, which can assist distribution network operators to make auxiliary decisions and improve the safety and efficiency of operators.
A Geomagnetic Road Localization Method Combining Coarse and Fine Matching
Authors: Luo Qinghua , Yu Mutong , Yan Xiaozhen , Liu Boyuan , Su Yuhao , Yang Longxin , Wang Lan
Published: December 2024

Geomagnetic navigation is a widely used positioning and navigation method that can eliminate the accumulated errors of inertial navigation systems, providing vehicles with long-distance, high-precision positioning. However, common geomagnetic road navigation algorithms such as DTW suffer from high computational complexity. Additionally, the low dimensionality of geomagnetic data features makes geomagnetic road navigation algorithms susceptible to measurement noise, making it difficult to improve positioning accuracy and reliability. To address these issues, this paper proposes a coarse-fine matching combined geomagnetic road positioning method. Firstly, when establishing the geomagnetic reference library, geomagnetic scalar and vector information are combined with attitude angle information to increase the feature dimensionality of the geomagnetic reference library. Secondly, Random Forest is used to perform coarse matching on data sequences to determine the current road, reducing the computational complexity of the geomagnetic road navigation algorithm. Finally, to further improve the efficiency of the geomagnetic road navigation algorithm and reduce the impact of random noise, Siamese Neural Network algorithm is employed to perform fine matching on data sequences, improving computational speed while ensuring positioning accuracy. Simulation experiments demonstrate that compared to the DTW algorithm, the root mean square error of the algorithm proposed in this paper is reduced from 64.21m to 43.83m, and the positioning time is reduced from 16.07s to 0.48s, indicating higher positioning accuracy and efficiency.
Hierarchical Equalization Control of Battery Pack Based on Reconfigurable Circuit
Authors: Jin Jianhua , Xia Xiaochun , Shi Yuchao , Wu Zhaoshun , Chen Xingyi
Published: December 2024

Lithium batteries have been widely used in the world, but cells connected in series will show inconsistency during operation, which greatly affects the performance and life of the battery pack. The main methods to solve battery pack inconsistency include active equalization and reconfigurable equalization. However, conventional reconfigurable equalization circuits can only equalize batteries when the battery pack is in the powered state, which imposes strict time constraints on battery pack equalization. Therefore, a new equalization control system with two-layer structure is built in this paper, where the bottom layer is an improved conventional reconfigurable circuit, and the top layer is a circuit composed of a flyback converter and switches. The hierarchical circuit proposed in this paper not only allows reconfigurable circuits to achieve equalization in a stationary state, so that sufficient equalized batteries are available before the reconfigurable batteries are powered up, but also enables direct equalization between any number of batteries, which greatly improves the equalization speed. Then, based on the circuit of this system, an equalization control strategy was designed in this paper, and MATLAB/Simulink was used to build a simulation to verify the effectiveness and superiority of the new control strategy.
Deep Learning-Based Method for Self-Explosion Defects Detection for Insulator on an Edge-Cloud Computing Infrastructure
Authors: Zhuang Qingtao , Liu Wanwei , Zhang Juan
Published: December 2024

Insulators play a critical role in power transmission and distribution networks and the inspection of insulator has been an important task. Given the demand for inspection efficiency and accuracy, a deep learning-based method for self-explosion recognition of insulators is proposed within a cloud-edge computing framework to enhance inspection efficiency and accuracy. A lightweight insulator detection model, based on YOLOv7-tiny, is introduced, specifically optimized for edge devices through modifications to its backbone architecture and loss function. In order to speed up the training process, SIOU are introduced into the loss function. Insulator areas are rapidly identified by the model, which then transmits the data to the cloud via 4G/5G networks for self-explosion identification. Additionally, a strategy for adjusting camera parameters is presented to improve image quality. Extensive experiments are conducted to demonstrate the high performance of the proposed method, affirming its effectiveness for real-time insulator inspection.
HEM Efficiency Comparison: Ethanol vs. Water in a Double Pipe Heat Exchanger Using Arduino Uno
Authors: Arifuzzaman Md. , Sayeduzzaman Md. , Hasan Kazi Emam Mahade
Published: December 2024

This research investigates the heat transfer efficiency of a double-pipe heat exchanger (DPHE) using ethanol and water as working fluids. The study focuses on the Heat Exchanger Metric (HEM) as an efficiency measure. It explores the effects of flow rates, inlet temperatures, and fluid properties on the system’s performance. Experimental setups were designed to simulate real-world applications, and data was collected using Arduino Uno microcontroller, temperature sensors, pressure sensors, flow rate sensors, and motor controllers. The HEM efficiency was calculated based on measured temperature and pressure differences. The findings of this research are expected to provide valuable insights into the performance of HEMs in double-pipe heat exchangers, particularly when considering alternative working fluids like ethanol. A counter-current flow arrangement was more efficient than a co-current flow arrangement. The research provides valuable insights for selecting the optimal working fluid in DPHE applications and contributes to understanding HEM as a reliable metric for evaluating heat exchanger performance.
A comparison of access strategies in all‐optical slotted WDM rings with switched delay lines
Authors: Ajmone Marsan M. , Bianco A. , Gibert Abos E. , Leonardi E.
Published: December 2024

The paper discusses the performance of access strategies for all‐optical packet networks based on a WDM multichannel ring topology with a number of synchronized slotted channels; nodes are equipped with one tunable receiver, one tunable transmitter, a variable number of delay lines and optical switches, and a FIFO transmission queue. Several access strategies based on local status information are described and compared, taking as performance indices packet loss probability, and maximum achievable throughput. We show that, among the considered proposals, the most efficient is a simple strategy that guarantees loss‐free transmission.
Optimal buffer allocation in ATM switches by effective cell loss
Authors: Ahn David S. , Lee Myung J.
Published: December 2024

One of the important issues in an ATM switch design is how to allocate the given buffer budget to ensure compliance with negotiated traffic contracts of each ATM connection. This problem owes mainly to the conflicting buffer requirements of different QoS parameters, such as cell loss, cell transfer delay, and cell delay variation. For example, increasing the buffer size of a connection at a switch may reduce cell loss due to buffer overflow, but the benefit of adding buffers possibly causes an excessive queueing delay due to increased buffer sizes. In this paper, such trade‐off issue in buffer allocation for different QoS requirements at a switch are quantified by a single nodal QoS parameter called Effective Cell Loss (ECL), in which both cell loss due to buffer overflow and cell loss due to excessive delay are properly integrated. The immediate benefit, among many others, of imposing ECL at switches is an optimal buffer allocation resulted by the conflicting buffer requirements of cell loss and cell delay parameter. Consequently, given the acceptable cell loss probability, the maximum cell delay tolerance, and the fixed buffer budget at an ATM switch, an optimal buffer allocation is found by minimizing ECL. Therefore, ECL is an effective QoS parameter that provides not only the most faithful way to comply with negotiated traffic contracts but also an optimal buffer allocation for a given buffer budget at a switch. Furthermore, we present the effectiveness of using ECL at a switch under nonuniform traffic arrival.
An efficient delay‐constrained multicast routing algorithm
Authors: Sun Quan , Langendörfer Horst
Published: December 2024

An efficient delay‐constrained multicast routing algorithm computing low cost delay‐constrained multicast trees with small algorithm complexity is proposed in this paper. The proposed algorithm can be used to compare cost performances of the existing or future multicast routing algorithms that provide quality of service (QoS) guarantees, especially in multicast routing simulation environments which simulate relatively large networks and consider realistic network conditions. The proposed algorithm is also useful for routing real‐time multicast data in high‐speed networks if adequate global information is available to the source.
Traffic modeling and QoS prediction for MPEG‐coded video services over ATM networks using scene level statistical characteristics
Authors: Yoo Sang‐Jo , Kim Seong‐Dae
Published: December 2024

In this paper, we propose a new traffic model and its queueing solution for MPEG‐coded video sequences, which are now widely used for many types of video applications. The MPEG variable bit rate (VBR) video traffic has both very strong short‐range correlations and long‐range dependence. To capture the long‐range dependence, we model the overall scene‐level cell rate flow with a scene‐level state transition diagram. At the same time, we use a frame‐level chain to reflect the short‐range correlation effects between the frames of the same frame type and between the different frame types within a scene state. Thus scene changes and frame sequences are modeled by a two‐dimensional continuous time Markov chain. We provide an analytic queueing solution in terms of the maximum cell transfer delay and the cell loss ratio. The simulation results show that our analytical model accurately approximates the queueing performance of the original videos. Finally, with an asymptotic approximation, we provide a method for estimating the effective bandwidth for MPEG video sources with a guarantee of the user’s quality of service requirements.
TCP Splice for application layer proxy performance
Authors: Maltz David A. , Bhagwat Pravin
Published: December 2024

Application layer proxies already play an important role in today’s networks, serving as firewalls and HTTP caches – and their role is being expanded to include encryption, compression, and mobility support services. Current application layer proxies suffer major performance penalties as they spend most of their time moving data back and forth between connections; context switching and crossing protection boundaries for each chunk of data they handle. We present a technique called TCP Splice that provides kernel support for data relaying operations which runs at near router speeds. In our lab testing, we find SOCKS firewalls using TCP Splice can sustain a data throughput twice that of normal firewalls, with an average packet forwarding latency 30 times less.
Performance modeling of a finite capacity polling system with ATM bursty and correlated input traffic
Authors: Jou Y. Frank , Nilsson Arne A. , Lai Fuyung
Published: December 2024

This paper is concerned with the mean delay and the probability of cell loss that bursty and correlated arrivals incur in an ATM switching system which can be modeled as a finite capacity polling system with nonexhaustive cyclic service. The arrival process to each input port of the system is modeled by a Markov Modulated Bernoulli Process (MMBP) which is able to describe the bursty and correlated nature of the ATM traffic. A practical polling system with finite capacity, as the one we deal with here, does not lend itself to an exact solution. In this paper, we introduce a tractable approach to provide an analytical approximation. This approach is validated extensively by comparing it against simulation results under different configurations. It is shown that both the mean delays and the cell loss probabilities obtained from this analysis provide highly accurate estimates.
Practical security issues with high‐speed networks[1]Presented at the 11th Annual Canadian Information Technology Security Symposium, 10–14 May 1999, Ottawa, Canada.
Authors: Velissarios John , Santarossa Roberto
Published: December 2024

As corporate networks evolve in step with the Internet, an increasing number of networks are being connected through controlled access points. The deployment of end‐to‐end high‐speed connections in corporate LANs have resulted in as yet untamed security issues directly attributable to the increased throughput (100+ Mbits/s). This paper attempts to identify some of the potential issues and communicate these to those responsible for the administration and development of IT and security infrastructures. Limitations of Intrusion Detection Systems, information leakage of encrypted channels, reduced features of hardware in order to enable faster switching, have all contributed to effectively diminish overall security. Despite the endless need for faster networks engendered by streaming video and audio, 3D worlds, voice over data and video conferencing, we must pause and ask ourselves if we are prepared to trade security for speed.
On bounds for the wavelength assignment problem on optical ring networks
Authors: Li Guangzhi , Simha Rahul
Published: December 2024

This research note presents two new bounds for the off‐line wavelength assignment problem in optical ring networks that use wavelength division multiplexing. In this context, we consider a well‐known bound [28,35] that, to our knowledge, remains the only published bound for a ring topology and for which examples exist that show tightness. In this note, we show the bound can be improved in two ways: (1) by considering an additional parameter (the number of network nodes), we provide a sharper bound than the existing bound, and (2) we extend a classic result in [35] that was proved for the special case of $k=3$ (no $k$ connections cover the ring) to the general case of arbitrary $k$ .
Dynamic token bucket (DTB): a fair bandwidth allocation algorithm for high‐speed networks
Authors: Kidambi Jayakrishna , Ghosal Dipak , Mukherjee Biswanath
Published: December 2024

Fair allocation of available bandwidth to competing flows is a simple form of quality of service (QoS) that can be provided to customers in public networks. A number of packet‐scheduling and buffer‐management techniques have been proposed in the literature to achieve this goal efficiently. However, the complexity of the existing algorithms prevents a high‐speed implementation with the current state of router technology. We propose a computationally simpler mechanism based on token‐bucket policing to achieve almost equal bandwidth allocation for a set of competing flows. The proposed method adjusts the token‐bucket threshold dynamically and measures the instantaneous arrival rate of flows. It uses this information to decide whether or not to admit a packet arriving at the network edge. With minor modifications, our framework can be used in a variety of practical network environments ranging from the Internet to virtual private networks (VPNs) over Frame Relay. We present a detailed simulation study that evaluates the performance of our algorithm. The simulation results indicate that DTB is fair, efficient, and robust.
Call admissibility for multirate traffic in wireless ATM networks
Authors: Biswas Subir K. , Sengupta Bhaskar
Published: December 2024

For multirate wireless ATM traffic, the first part of the call admission process is to determine whether to admit calls as long as bandwidth is available or to deny admission to a call of a particular class even if there is enough bandwidth available, in the hope of admitting calls of some other class later. A second part of the process is to determine if the quality of service requested by the call can be met. A scenario in which the first part is particularly important is when the blocking probability requirements for different classes is different. In this paper, we consider four policies to determine the circumstances under which calls of different types are admissible. For each of these policies, we show how to compute the blocking probabilities. For three of these policies, the blocking probabilities can be found by using results from product form networks. For the fourth, we provide an approximation which works extremely well in practice. We also formulate a non‐linear programming problem which attempts to determine the parameters of the admissibility policies in such a way to maximize the call arrival rates while keeping the blocking probabilities under specified bounds. We provide an algorithm for solving the non‐linear programming problem and use this as a basis for comparing the policies. We show that under some circumstances, it is possible to improve the system throughput by as much as 35% by a suitable use of the admissibility policies. This improvement in throughput is particularly important in wireless ATM networks, supporting high rate multimedia traffic because of the inherent limitations in bandwidth availability.
On a class of time varying shapers with application to the renegotiable variable bit rate service
Authors: Giordano Silvia
Published: December 2024

A shaper is a system that stores incoming bits in a buffer and delivers them as early as possible, while forcing the output to be constrained with a given arrival curve. A shaper is time invariant if the traffic constraint is defined by a fixed arrival curve; it is time varying if the condition on the output is given by a time varying traffic contract. This occurs, for example, with renegotiable variable bit rate (RVBR) services. We focus on the class of time varying shapers called time varying leaky bucket shapers; such shapers are defined by a fixed numbers of leaky buckets, whose parameters (rate and bucket size) are changed at specific transition moments. We assume that the bucket levels are kept unchanged at those transition moments (‘no reset’ assumption). Our main finding is an input‐output characterisation for this class of time varying shapers. Then we apply it to the tradeoff in optimising the RVBR service, assuming that a perfect prediction of future traffic can be made. We provide two algorithms that solve the problem of finding, at any renegotiation, the parameters for a RVBR service, respectively when the knowledge of the input traffic is limited to the next interval (local optimisation problem) and when we dispose of the complete input traffic description (global optimisation problem). We compare, by means of simulation, the two resulting algorithms to study the validity of the local approach. We illustrate the impact of the ‘no‐reset’ assumption by analyzing on some examples the losses that occur when the source chooses the opposite approach, namely, the ‘reset’ approach. Furthermore we simulate the RVBR service versus the renegotiable constant bit rate (RCBR) service and illustrate that the RVBR approach can provide substantial benefits. Finally, we discuss the impact of the size of the renegotiation interval on the efficiency of the RVBR service.
Optimal transmission schedule in WDM optical networks with multiple transmitters and receivers
Authors: Lee Sang‐Kyu , Oh A. Duksu , Choi Hyeong‐Ah
Published: December 2024

In this paper, we study the problem of optimal transmission schedules for embedding complete graphs in WDM broadcast‐and‐select optical networks. An optimal transmission schedule is defined to be the one that schedules transmissions such that each node transmits once to every other node within a repeating cycle of minimum length. Our model assumes that the network has N nodes with k wavelength channels, and each node is equipped with α tunable transmitters and β fixed‐tuned receivers. Given α, β (1≤α,β≤k) and δ (tuning delay required for a transmitter to tune from one wavelength to another), we develop an optimal transmission schedule with schedule length max {αβN(N−1)/k, β(N−1)+kδ} such that each transmitter of each node transmits once to each receiver of its neighboring nodes within this time period.
On tolerating single link, double link, and nodal failures in symmetric grid networks
Authors: Acampora Anthony S. , Gholmieh Ralph A. , Krishnamurthy Srikanth
Published: December 2024

In this paper, we consider a symmetric grid network consisting of N distinct nodes. The number of allowable calls (either the number of circuit switched calls or the maximum number of virtual connections such that QoS objectives are maintained) between any two nodes of the network is assumed to be a constant. We first determine this constant assuming that the network is fully loaded. Then, we find the maximum additional capacity needed on each link such that single link, and double link failures can be tolerated by rerouting calls around failed links. Results show that the maximum additional capacity needed to recover from any single link, double link, or single node failure, with no loss of connections (except for those connections terminating at a failed node) scales as ${1/\sqrt{(N)}}$ . Thus, we conclude that rerouting, combined with an admission policy which blocks new call attempts such that a fraction of capacity proportional to ${1/\sqrt{(N)}}$ is reserved for failure recovery, provides totally failsafe operation in the presence of such failure events.
An efficient algorithm for reducing the number of Add‐Drop Multiplexers in SONET/WDM rings
Authors: Li Guangzhi , Simha Rahul
Published: December 2024

This paper considers a network design problem introduced by Gerstel, Lin and Sasaki (INFOCOM'98) in which resource allocation is performed within a Wavelength Division Multiplexing (WDM) optical ring network to reduce overall equipment cost. The problem can be summarized as follows. The Add‐Drop Multiplexers (ADM's) that are used to terminate lightpaths in an optical (SONET/SDH) ring are expensive. A naive implementation would require ADM's for each wavelength at each node. However, by carefully assigning connections to wavelengths and routing the resulting lightpaths, one may avoid terminating all wavelengths at every node, and thereby reduce the number of ADM's needed.

While Gerstel et al. consider wavelength assignment with respect to this problem, they do not consider the additional complication of routing. In this paper, we consider joint routing and wavelength assignment, and show that the number of ADM's required is significantly less than the number resulting from applying the heuristics in Gerstel et al. Our algorithm analyzes connection requirements and, using a decomposition based on Euler paths, performs routing and wavelength assignment.
Robust TCP congestion recovery
Authors: Wang Haining , Shin Kang G.
Published: December 2024

This paper presents a new robust TCP congestion‐recovery scheme to (1) handle bursty packet losses while preserving the self‐clocking capability; (2) detect a TCP connection's new equilibrium during congestion recovery, thus improving both link utilization and effective throughput; and (3) make the TCP behavior during congestion recovery very close to that during congestion avoidance, thus “extending” the performance model for congestion avoidance to that for TCP loss recovery. Moreover, the new recovery scheme requires only a slight modification to the sender side of TCP implementation, thus making it widely deployable. The performance of the proposed scheme is evaluated for scenarios with many TCP flows under the drop‐tail and RED gateways in the presence of bursty packet losses. The evaluation results show that the new scheme achieves at least as much performance improvements as TCP SACK and consistently outperforms TCP New‐Reno. Furthermore, its steady‐state TCP behavior is close to the ideal TCP congestion behavior. Since the proposed scheme does not require selective acknowledgments nor receiver modifications, its implementation is simpler than SACK, and only the servers in the Internet need to be modified while keeping intact millions of clients scattered in the Internet.
A detailed performance analysis of UDP/IP, TCP/IP, and M‐VIA network protocols using Linux/SimOS
Authors: Won Chulho , Lee Ben , Yu Chansu , Moh Sangman , Park Kyoung , Kim Myung‐Joon
Published: December 2024

This paper presents a performance study of UDP/IP, TCP/IP, and M‐VIA using Linux/SimOS. Linux/SimOS is a Linux operating system port to a complete machine simulator SimOS. A complete machine simulator includes all the system components, such as CPU, memory, I/O devices, etc., and models them in sufficient detail to run an operating system. Therefore, a real program execution environment can be set up on the simulator to perform detailed system evaluation in a non‐intrusive manner. The motivation for Linux/SimOS is to alleviate the limitations of SimOS (and its variants), which only support proprietary operating systems. Therefore, the availability of the popular Linux operating system for a complete machine simulator will make it an extremely effective and flexible simulation environment for studying all aspects of computer system performance, especially evaluating communication protocols and network interfaces. The contributions made in this paper are two‐fold: First, the major modifications that were necessary to run Linux on SimOS are described. These modifications are specific to SimOS I/O device models and thus any future operating system porting efforts to SimOS will experience similar challenges. Second, a detailed analysis of UDP/IP, TCP/IP, and M‐VIA is performed to demonstrate the capabilities of Linux/SimOS. The simulation study shows that Linux/SimOS is capable of capturing all aspects communication performance, including the effects of the kernel, device driver, and network interface.
A new approach for path capacity measurement in Internet
Authors: Lin Yu , Cheng Shiduan , Wang Chonggang , Wu Haitao , Long Keping , Zou Shihong
Published: December 2024

The p‐pair/train technique estimates the capacity of a path from the dispersion experienced by two/multiple back‐to‐back packets. The dispersion of packets may follow a complicated multimodal distribution, which causes statistical filtering methodologies and heuristic approaches (e.g., pathrate) to be inaccurate in heavily‐loaded cases. This paper analyzes the noise characteristics in the path capacity measurement, and elaborates on the distribution of capacity estimates. Based on this analysis, a new algorithm called LMSA (Local Modes Statistical Algorithm), and its enhancement (LMSA+) are presented. Using multiple distributions of capacity estimates obtained by variable‐sized probing p‐pairs, LMSA+ only picks out the local modes that locates at fixed positions, and selects the minimum of these modes as the path capacity. Simulation results demonstrate that, compared with pathrate, LMSA+ is more accurate in heavily‐loaded paths or paths with relatively large bottleneck bandwidth values, and is more robust to the dynamic cross traffic load.
Benefits of partial reconfigurability in circuit-switched WDM networks
Authors: Martin James
Published: December 2024

We describe and study partially reconfigurable circuit-switched networks. These are dynamic networks in which partial, but not complete, flexibility of resource assignment is retained during the lifetime of a connection. In particular we analyse two examples of partially reconfigurable WDM networks with flexibility of wavelength assignment. In the first example, each connection in the network requires a main lightpath (whose wavelength must remain fixed) and a standby lightpath (whose wavelength may change). In the second example, the network contains two classes of connections with different service levels, one class reconfigurable and the other not. We propose two contrasting reconfiguration algorithms, and demonstrate that even a small amount of reconfigurability can yield significant performance gains, while a large amount of reconfigurability yields almost all the performance gain that would be attained by introducing complete wavelength conversion to the network.
A lookup algorithm based on multiple tables for high-speed routers
Authors: Kim Kyungjun , Han Kijun
Published: December 2024

The IP address lookup in the communication link technologies is becoming a major bottleneck by exploring the exact matching and the parallel hashing in each prefix length. In this paper, we present an algorithm for IP address lookup and collision resolution to reduce memory space and solve collision for high speed routing based on multiple table indexing structure. Our scheme makes possible direct access in a designated IP prefix without replicating the forwarding table entries, and provides efficient collision resolution for fast route lookup with only small memory. Simulation results indicate that our algorithm provides a faster lookup than the conventional lookup schemes.
Two priority buffered multistage interconnection networks
Authors: Shabtai Galia , Cidon Israel , Sidi Moshe
Published: December 2024

This paper presents a novel architecture of internally two priority buffered Multistage Interconnection Network (MIN). First, we compare by simulation the new architecture against a single priority MIN and demonstrate up to N times higher throughput for the high priority traffic in a hot spot situation, when N is the number of inputs. In addition, under uniform traffic assumption we show an increase in the low priority throughput, without any change in the high priority throughput. Moreover, while in the single priority system the high priority delay and its standard deviation are increased when low priority traffic is present, it is kept constant in the dual priority system. Finally, we introduce a new approach of long Markovian memory performance model to better capture the packets dependency in a single priority MIN under uniform traffic and extend this model for a dual priority MIN. Model results are shown to be very accurate.
ROBS: A novel architecture of Reliable Optical Burst Switching with congestion control
Authors: Luo Jiangtao , Huang Jun , Chang Hao , Qiu Shaofeng , Guo Xiaojin , Zhang Zhizhong
Published: December 2024

In this paper, we propose a novel improved architecture of Optical Burst-Switched Networks, called Reliable Optical Burst Switching (ROBS), which introduces congestion control and retransmission mechanisms of TCP to OBS layer. Design issues of edge and core nodes for ROBS networks are both demonstrated. Part of its function has been implemented on ns-2 platform and its performance are evaluated by simulation.
An empirical performance analysis of minimal and non-minimal routing in cube-based OTIS multicomputers
Authors: Najaf-abadi Hashem Hashemi , Sarbazi-Azad Hamid
Published: December 2024

In this study, the performance of virtual cut-through switching in the cube-based OTIS architecture, an optoelectronic interconnection architecture for multicomputer systems, is empirically analyzed. Deadlock-free deterministic and adaptive minimal path routing algorithms for this architecture are introduced, and the effects of different network and traffic parameters on average message latency are investigated. This analysis presents a relatively more realistic view of the OTIS architecture than that presented in previous work by considering issues related to a lower level of abstraction (the routing and switching of messages). Among other results, the analysis indicates that depending on the traffic pattern, minimal path routing in these architectures may cause extreme congestion to occur over certain channels of the network, resulting in severe performance degradation. Alternative non-minimal path routing schemes are therefore suggested and their performance compared. One of the non-minimal approaches suggested is found to be able to sustain at least half the maximum possible bandwidth under all studied traffic patterns. Yet determining a single routing algorithm that is capable of attaining the highest possible throughput for all different traffic patterns remains an open problem. A constraint-based analysis of the effect of dimensionality on performance is also conducted.
Stochastic model for cell movement in a knockout switch in computer networks
Authors: Shukla Diwakar , Gadewar Surendra
Published: December 2024

In computer networks, switching is used as a juncture to provide a path to a message to pass on. The knockout switch is a specially designed architecture having equal number of input and output lines. An input cell, in this switch, passes through several stages like filters, concentrators and shifters (or queue). The cell may be under unicasting or multicasting depending upon the number of tokens of output lines allotted. This paper considers the random movement of a cell, inside the design of knockout switch, up to the output line. A Markov chain model is proposed to explain the transitions on various states of filter, concentrator and shifter. The outgoing probability is computed using the number of transitions performed by the cell. Several theorems and corollaries are derived for explaining the behavior of the cell movement. The expected number of transitions are computed keeping various situational constraints. A simulation study is performed to support the derived theorems under the model.