Affect System Performance Research Articles

An Agent-Based Model of Miscommunication in Complex System Engineering Organizations

Communication in engineering organizations affects the performance of the complex systems they design. Miscommunication occurs when communication results in a “deficiency” or “problem” that hinders parties from fulfilling their individual or collective values. A recent study demonstrated widespread miscommunication in a Fortune 500 engineering firm about the definition of “an estimate” in a complex system design context. Building on that work, this article used a Monte Carlo simulation (8800 runs) of an agent-based model to demonstrate how systemic design process miscommunication may affect complex system performance. Each run of the simulation created a unique 1000-artifact system using a network generation algorithm and converged its design through optimization. Systems where estimates communicated “current” designs outperformed systems where estimates communicated “future” projections of their designs instead. Varying the fraction of the population, which uses each definition of an estimate varied system performance and uncertainty. Whether related to estimate definitions or more generally, this article demonstrates that miscommunication may affect system performance.

Efficient Tracing Methodology Using Automata Processor

Tracing or trace interface has been used in various ways to find system defects or bugs. As embedded systems are increasingly used in safety-critical applications, tracing can provide useful information during system execution at runtime. Non-intrusive tracing that does not affect system performance has become especially important, but unfortunately, the biggest obstacle to this approach was the vast amount of real-time trace data, making it challenging to address complex requirements with relatively limited hardware implementations. Automata processors can be programmed with a memory-like structure of automata and have a structure specific to streaming data, large capacity, and parallel processing functions. This paper promotes the idea of high-level system-on-chip monitoring using automata processors. We used a safety-critical pacemaker application in the experiments, described timed automata (TA)-based requirements, and tested intentionally injected 4,000 random failures. The TA model converted for Automata Processor to monitor system, correctness, and safety properties achieved 100% failure detection rate in the experiment, and the detected failure is reported as fast enough to allow enough extent for failure recovery.

Biometric Systems Interaction Assessment: The State of the Art

The design and implementation of effective and efficient biometric systems presents a series of challenges to information technology (IT) designers to ensure robust performance. One of the most important factors across biometric systems, aside from algorithmic matching ability, is the human interaction influence on performance. Changes in biometric system paradigms have motivated further testing methods, especially within mobile environments, where the interaction with the device has fewer environmental constraints, which may severely affect system performance. Testing methods involve the need for reflecting on the influence of user-system interaction on the overall system performance in order to provide information for design and testing. This paper reflects on the state of the art of biometric systems interaction assessment, leading to a comprehensive document of the relevant research and standards in this area. Furthermore, the current challenges are discussed and thus we provide a roadmap for the future of biometrics systems interaction research.

Modeling and optimization of a combined cooling, cascaded power and flue gas purification system in marine diesel engines

The severe energy crisis and environmental deterioration we face today requires the development of novel methods to control emissions and enhance energy savings. In this investigation, based on the thermodynamic theory, a combined system including a dual-loop organic Rankine cycle, absorption refrigeration, and flue gas purification is modeled. The system can use various forms of waste heat to realize cascade utilization. Initially, through comparisons with existing experimental data, we verified the accuracy of the numerical simulation. The parameters affecting system performance are analyzed and discussed comprehensively. In addition, considering the contribution of the refrigeration system, a genetic algorithm is used to calculate the equivalent system output power. The optimized equivalent output power, thermal efficiency, and exergy efficiency are calculated as 1668.47 kW, 59.6%, and 57.29%, respectively. The results of the emission reduction analysis indicate that the purification system exhibits excellent removal performance with a desulfurization and denitrification efficiency of 99.8% and 45.52%, respectively, and the energy regulatory metrics meet the 2020 emission requirements. Therefore, this novel design can be considered as a feasible method to resolve energy inefficiency and emission reduction in ships.

Experimental investigation of the impact of lubricant oil ratio on subcritical organic Rankine cycle for low-temperature waste heat recovery

Organic Rankine cycle can be used to harness waste heat to generate electricity. The cycle performance is dependent on expander behavior, where the design of lubricant oil loop is significant. The effects of oil on expansion machine rely on the prevention of leakages and friction losses. However, the lubricant oil is inevitably mixed with refrigerant, which may in turn affect system performance. This paper is targeted to investigate the impact of lubricant oil ratios on a 2 kW ORC prototype using R245fa as working fluid. The heat source temperature is fixed at 125 °C. Two degrees of freedom including the mass flow rate and expander rotational speed are adjusted to explore the system performance. Cycle thermal efficiency, expander isentropic efficiency, filling factor and heat transfer performance are analyzed. The results show that injection of lubricant oil has significant influence on the organic Rankine cycle system. The optimum cycle thermal efficiency is 4.7%, which is obtained under high oil ratio. The system efficiency is more sensitive under lower lubricant oil charges, as 10.25% increase in cycle thermal efficiency is observed when oil-concentration varies from 0.12% to 1%. The hermetic scroll expander is more sensitive to various oil-concentration than the plate heat exchanger.

NV-eCryptfs: Accelerating Enterprise-Level Cryptographic File System with Non-Volatile Memory

The development of cloud computing and big data results in a large amount of data transmitting and storing. In order to protect sensitive data from leakage and unauthorized access, many cryptographic file systems are proposed to transparently encrypt file contents before storing them on storage devices, such as eCryptfs. However, the time-consuming encryption operations cause serious performance degradation. We found that compared with non-crypto file system EXT4, the performance slowdown could be up to 58.53 and 86.89 percent respectively for read and write with eCryptfs. Although prior work has proposed techniques to improve the efficiency of cryptographic file system through computation acceleration, no solution focused on the inefficiency working flow, which is demonstrated to be a major factor affecting system performance. To address this open problem, we present NV-eCryptfs, an asynchronous software stack for eCryptfs, which utilizes NVM as a fast storage tier on top of slower block devices to fully parallelize encryption and data I/O. We design an efficient NVM management scheme to support the fast parallel cryptographic operations. Besides providing an address space that can be directly accessed by the hardware accelerators, our designed mechanism is able to record the memory allocation states, and supplies a backup plan to deal with the situation of NVM shortage. The additional index structure is built to accelerate lookup operations to determine if a given data block resides in NVM. Moreover, we integrate an adaptive scheduling in NV-eCryptfs to process I/O requests dynamically according to access pattern and request size, which is able to take full utilization of both software and hardware acceleration to boost crypto performance. Our evaluation shows the proposed NV-eCryptfs outperforms the original eCryptfs with software routine 23.41× and 5.82× respectively for read and write.

(Invited) Design Consideration of an IGFC System with CO2 Capture

Due to vast coal reserve and its lower cost, integrated Gasification Combined Cycle (IGCC) and Integrated Gasification Fuel Cell (IGFC) power generation system are being developed to use coal effectively and reduce air pollution. Compared to IGCC, the advantage of IGFC is higher efficiency and lower overall cost, especially pressurized system. An IGFC system is being developed using syngas as fuel with CO2 capture at National Institute of Clean Low-Carbon Energy (NICE). In the system, the high temperature solid oxide fuel cell (SOFC) stacks are used to convert fuel to electricity. The system design principles, syngas composition and SOFC stack performance effect on system efficiency, and the system cost will be discussed, estimated, and analyzed based on the model established. The method of CO2 capture will also be discussed and recommended based on experimental data. There is variety of impurities in syngas, such as sulfur, PH3, Siloxane, chlorine, Arsine, etc, which may poison SOFC anode and significantly affect system performance. Syngas cleaning is needed before powering the stack using syngas. Besides, there is significant amount of CO2 in initial syngas which will dilute flammable H2 concentration which may affect both power generation and the efficiency of the system, which eventually resulted in higher cost. Two syngas cleaning methods were evaluated and recommendation was made based on experimental results. Syngas composition may vary based on the cleaning method to be used. The CO in syngas has two potential negative effects on SOFC operation. First, the Boudouard reaction is of concern in the temperature range from 500 to 600oC when CO can dissociate into C and CO2 (equation 1), which is called carbon coking. The method to prevent carbon coking was discussed. Second, if dry syngas is used as fuel, the water-gas shift reaction (equation 2) may occur in SOFC stack with the accumulation of water steam formation from electrochemical reaction, which is exothermic. The heat release from water-gas shift reaction would increase temperature difference between stack inlet and outlet which make it difficult to manage stack temperature to achieve optimized performance. SOFC stack electrical efficiency was analyzed with different fuel compositions and under different designed operation conditions, such as anode recycle ratio, using the model established. CO ↔ CO2 + C (1) CO + H2O ↔ H2 + CO2 (2) In order to capture CO2 from exhaust fuel gas, CO2 has to be concentrated higher than 98% first in the tail gas. Technical approaches were identified. Small scale matrix tests show promising results to meet expectation. Fabrication of scale-up testing equipment for technology verification is in process.

Adaptive model predictive control for hybrid energy storage energy management in all-electric ship microgrids

Hybrid energy storage systems have been widely used in transportation, microgrid and renewable energy applications to improve system efficiency and enhance reliability. However, parameter uncertainty can significantly affect system performance. In order to address this issue, an adaptive model predictive control is developed in this paper. Online parameter identification is used to mitigate parameter uncertainty, and model predictive control is used to optimally split power, deal with constraints, and achieve desired dynamic responses. A sensitivity analysis is conducted to identify major impact factors. In order to validate the proposed method, both simulation and experiments are performed to show the effectiveness of the proposed adaptive model predictive control. Compared to the model predictive control without online parameter identification, the power loss reduction can be as high as 15% in the experiments. This study focuses on all-electric ship energy management to mitigate load fluctuations and improve system efficiency and reliability. The proposed method could also be used in other applications.

Relative Vehicle Displacement Approach for Path Tracking Adaptive Controller With Multisampling Data Transmission

This paper proposes a cyber-physical framework for vision-based automated vehicle path tracking. The framework has been developed in two parts: first, an intelligent relative vehicle displacement approach with an adaptive neural network controller; and second, multisampling data transmission architecture for any sensor–controller–actuator network. Uncertainties due to illumination effects, occlusion, and obscure images affect system performance drastically. The proposed relative vehicle displacement approach takes care of these uncertainties. The adaptive neural network controller generates precise control actions for stabilizing the system in minimum time. A reliable and robust data transmission architecture is of utmost importance for any Internet of Things application. Successful data transmission depends on several parameters, such as delay, communication channel behavior, and packet loss. A novel multisampling data transmission architecture addressing these issues has been proposed in this paper. Various cases of data transmission have been demonstrated on the time critical application of vision-based tracking by an automated guided vehicle. The results of real-time path tracking operation have been duly compared with other control techniques and data transmission architecture. The experimental results show the efficiency of the proposed system.

Insights into the effects of carbon source on sequencing batch reactors: Performance, quorum sensing and microbial community.

Effects of carbon source on the performance, quorum sensing (QS) and microbial communities in the sequencing batch reactors were investigated in this work. Among the chosen carbon source, sodium acetate (R1), glucose (R2), starch (R3) and Tween 80 (R4), sodium acetate was the best carbon source for nutrient removal, while starch was favorable for inducing the sludge bulking, and Tween 80 was beneficial to the production of extracellular polymeric substances (EPS) and proliferation of Microthrix parvicella. Additionally, the R2 value of linear correlation between sludge settleability and particle size in four reactors followed an order of R1 > R2 > R3 > R4. Moreover, Person correlation analysis showed that various significant correlations were observed in reactors fed with different carbon sources and the QS mainly mediated the production and component of EPS. High-throughput sequencing analysis revealed that the carbon source affected microbial communities and the Canonical correspondence analysis results indicated that QS related to microbial communities. It was inferred that the interactions between microbial communities and QS affected system performance.

Memory Partitioning and Management in Memcached

Memcached is a popular component of modern Web architectures, which allows fast response times–a fundamental performance index for measuring the Quality of Experience of end-users–for serving popular objects. In this work, we study how memory partitioning in Memcached works and how it affects system performance in terms of hit ratio. We first present a cost-based memory partitioning and management mechanism for Memcached that is able to dynamically adapt to user requests and manage the memory according to both object sizes and costs. We present a comparative analysis of the vanilla memory management scheme of Memcached and our approach, using real traces from a major content delivery network operator. We show that our proposed memory management scheme achieves near-optimal performance, striking a good balance between the performance perceived by end-users and the pressure imposed on back-end servers. We then consider the problem known as “calcification”: Memcached divides the memory into different classes proportionally to the percentage of requests for objects of different sizes. Once all the available memory has been allocated, reallocation is not possible or limited. Using synthetic traces, we show the negative impact of calcification on the hit ratio with Memcached, while our scheme, thanks to its adaptivity, is able to solve the calcification problem, achieving near-optimal performance.

An Observer-Backstepping Robust Controller Design Method

Unmodeled dynamics and external disturbances are the main factors affecting system performance. In this paper, a robust design method based on backstepping control and observer is proposed to overcome the problem of the system unmodeled parts and external disturbances. To improve the performance, the controller uses adaptive function to eliminate the effect of the unmodeled dynamics. For the external disturbances, this paper using observer to accurately estimated and effectively compensated. The simulation results show that the controller designed in this paper has good performance and can accurately response the input commands in the case of the unmodeled part of the system and the external disturbance.

Performance analysis of opportunistic beamforming system under non‐identical imperfect channel environment

In this study, the authors study the effect of non-identical channel estimation error and feedback delay on the performance of an opportunistic beamforming system. This study derives the exact system performance (i.e. outage probability, symbol-error rate (SER), and ergodic capacity) of the proposed system using moment generating function in an imperfect channel environment. This study also uses an asymptotic analysis to quantify the diversity order of SER and outage probability to analyse which system variables affect system performance. From the results of an asymptotic analysis, it is shown that by channel estimation error and feedback delay, spatial diversity is eliminated, but the benefits of multiuser diversity still exist. Therefore, the diversity order of the SER and the outage probability of the proposed system are proportional to the number of user terminals, but the conventional system is limited to 1 by channel estimation error and feedback delay.

Life Cycle Assessment of Low-Rank Coal Utilization for Power Generation and Energy Transportation

In China, the electricity load is concentrated in the east, but low-rank coal resources are concentrated in the west. To solve this contradiction, in this study, three cases for energy transmission about power system with and without solar energy were studied by life cycle assessment (LCA). Case 1 directly combusts low-rank coal to generate electricity in western China and transmits it to eastern China by grid. Cases 2 and 3 upgrade low-rank coal and transport it to eastern China for power generation. With the evaluating indicators and various stages of LCA, the impact of each case on the environment was compared clearly. The results show that over 90% of the pollutant emission comes from coal combustion throughout the life cycle. The pollutant emission of upgraded coal transportation is less than 5%. With low-rank coal upgrading then combusting, the total emission is less than that of direct combustion. In particular, with solar energy added, the emission of combustion can be further reduced. On the bases of LCA, analytic hierarchy process (AHP) was used to establish the connection of these four evaluation indicators to comprehensively evaluate the performance of the three cases through the objective function of AHP, which provided guidance for the energy transmission and utilization in the eastern and western China. Finally, sensitive analysis shows the main major factors affecting system performance on the system. The results show that the Case 3, which integrates with solar energy, performs best in the whole life scale.

Data-Aided Frequency Offset Estimation for CE-OFDM Broadband Satellite Systems

In recent years, the constant-envelope orthogonal frequency-division multiplexing (CE-OFDM) has been considered as a candidate waveform in broadband satellite systems as it has a 0-dB peak-to-average power ratio (PAPR). However, the carrier frequency offset (CFO) estimation scheme for CE-OFDM broadband satellite systems directly affects system performance. In this paper, we analyze the network architecture and the propagation environment of CE-OFDM broadband satellite systems, and we propose a data-aided CFO estimation strategy based on the frequency domain pilot symbols. The Cramer–Rao bound (CRB) of our CFO estimator is given by mathematical analysis, and the effect of the number of pilot symbols on the estimation performance is analyzed. The pilot symbol-based CFO estimator is composed of a phase demodulator and a discrete Fourier transform (DFT) module, and it can obtain a large estimation range under a small pilot overhead. The simulation results show that the CE-OFDM broadband satellite systems can achieve a good bit error rate (BER) performance by using the proposed strategy to estimate and compensate the CFO.

Security Analysis of Grr Rapid Response Network using COBIT 5 Framework

Connection from the Internet is required to always be maintained under any conditions, but not always connectivity will run smoothly, lots of crowds or problems that require connections do not run smoothly. Application of security systems to overcome all problems and difficulties, both technical and non-technical which can affect system performance. GRR Rapid Response is the answer to internet network security. GRR asks for a client-server model, agents installed on the machine (client) to be able to communicate with the Grr server to access and provide unique client IDs. After setting this active and running, the server can send a request to the client who collects information, and the client sends a response to the request. After Grr is made, it is necessary to do a system evaluation and evaluation. The COBIT 5 framework is a good standard for determining the level of maturity of network security. The maturity level obtained is 2.899 can be decided at an institutional maturity level defined. The level of support the institution has agreed to, supports and supports all activities related to network security.

Autonomous Landing of a Micro Aerial Vehicle on a Moving Platform Using a Composite Landmark

In the existing vision-based autonomous landing systems for micro aerial vehicles (MAVs) on moving platforms, the limited range of landmark localization, the unknown measurement bias of the moving platform (such as wheel-slip or inaccurate calibration of encoders), and landing trajectory knotting seriously affect system performance. To overcome the above shortcomings, an autonomous landing system using a composite landmark is proposed in this paper. In the proposed system, a notched ring landmark and two-dimensional landmark are combined as an R2D landmark to provide visual localization over a wide range. In addition, the wheel-slip and imprecise calibration of encoders are modeled as the unknown measurement bias of the encoders and estimated online via an extended Kalman filter. The landing trajectory is planned by a solver as a convex quadratic programming problem in each control cycle. Meanwhile, an iterative algorithm for adding equality constraints is proposed and used to verify whether the planned trajectory is feasible or not. The simulation and actual landing experiment results verify the following: the visual localization with the R2D landmark has the advantages of wide localization range and high localization accuracy, the pose estimation result of the moving platform with unknown encoder measurement bias is continuous and accurate, and the proposed landing trajectory planning algorithm provides a continuous trajectory for reliable landing.

Assessing public transit performance using real-time data: spatiotemporal patterns of bus operation delays in Columbus, Ohio, USA

ABSTRACTPublic transit vehicles such as buses operate within shared transportation networks subject to dynamic conditions and disruptions such as traffic congestion. The operational delays caused by these conditions can propagate downstream through scheduled transit routes, affecting system performance beyond the initial delay. This paper develops an approach to measuring and assessing vehicle delay propagation in public transit systems. We fuse data on scheduled bus service with real-time vehicle location data to measure the originating, cascading and recovery locations of delay events across space with respect to time. We integrate the resulting patterns to construct stop-specific delay propagation networks. We also analyze the spatiotemporal patterns of propagating delays using parameters such as 1) transit line-based network distance, 2) total propagating delay size, and 3) distance decay. We apply our methodology using publicly available schedule and real-time location data from the Central Ohio Transit Authority (COTA) public bus system in Columbus, Ohio, USA. We find that delay initiation is spatially and temporally uneven, concentrating on specific stops in downtown and specific suburban locations. Core stops play a critical role in propagating delays to a wide range of connected stops, eventually having a disproportional impact on the on-time performance of the bus system.

Photonic generation of frequency 16-tupling Millimeter wave signal using polarization property without an optical filter

In this paper, a novel filter free method of generating 16 tupled millimeter wave signal using polarization property is proposed. Phase modulators utilized in this scheme are independent of bias voltage deviation and have higher extinction ratio thus ensuring higher quality of generated mm wave signal. A large frequency tunable range is achievable, as no optical filter is used. A 160 GHz microwave signal is obtained at the polarizer output when a 10GHz RF local oscillator is employed, which is 16 folds the RF drive signal. The simulation results show that the generated signal offers an Optical Sideband Suppression Ratio (OSSR) of 63dB and Radio Frequency Spurious Suppression Ratio (RFSSR) of 51dB. The sideband suppression ratios obtained in the proposed scheme is higher than the previously suggested schemes on microwave signal generation using polarization property. Theoretical computations validate the simulation results. Various parameters affecting system performance are analyzed in later sections.

Aquifer Thermal Energy Storage (ATES) smart grids: Large-scale seasonal energy storage as a distributed energy management solution

Aquifer Thermal Energy Storage (ATES) is a building technology used to seasonally store thermal energy in the subsurface, which can reduce the energy use of larger buildings by more than half. The spatial layout of ATES systems is a key aspect for the technology, as thermal interactions between neighboring systems can degrade system performance. In light of this issue, current planning policies for ATES aim to avoid thermal interactions; however, under such policies, some urban areas already lack space for the further development of ATES, limiting achievable energy savings. We show how information exchange between ATES systems can support the dynamic management of thermal interactions, so that a significantly denser layout can be applied to increase energy savings in a given area without affecting system performance. To illustrate this approach, we simulate a distributed control framework across a range of scenarios for spatial planning and ATES operation in the city center of Utrecht, in The Netherlands. The results indicate that the dynamic management of thermal interactions can improve specific greenhouse gas savings by up to 40% per unit of allocated subsurface volume, for an equivalent level of ATES economic performance. However, taking advantage of this approach will require revised spatial planning policies to allow a denser development of ATES in urban areas.