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Non-standard tests for process control in chemically bonded sands

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China Foundry 2016年第1期13卷 59-66页

作者： S.Ramrattan department of Engineering Design Manufacturing and Management Systems Western Michigan University

Chemically bonded sand cores and molds are more commonly referred to as precision sand systems in the high production automotive powertrain sector. Their behavior in contact with molten metal can lead to casting defects. Consequently, the interaction is of great interest and an important part of metal casting technology. The American Foundry Society(AFS) sand testing is based on physical, mechanical, thermal and chemical properties of the sand system. Foundry engineers have long known that certain AFS sand tests provide limited information regarding control of molding and casting quality. The inadequacy is due to the fact that sand casting processes are inherently thermo-mechanical, thermo-chemical and thermo-physical. Non-standard foundry sand testing has proven useful for laboratory measurement of these characteristics in foundry sand using a disc-shaped specimen. Similarly, the equivalent disc-shaped specimens are used for casting trials. In order to accomplish near-net-shape casting with minimal defects, it is necessary to understand both the properties of the sand system, as well as the interface of molten metal when different binders, additives and/or refractory coatings are used. The methodology for the following non-standard chemically bonded sand tests is described:(1) disc transverse;(2) impact;(3) modified permeability;(4) abrasion;(5) thermal distortion;(6) quick loss on ignition. The data related to the non-standard sand tests were analyzed and interpreted. The test results indicate that there is relatively lower test-to-test variability with the disc-shaped specimens. The non-standard tests were able to discriminate between the chemically bonded polyurethane cold box sand specimens. Further studies should be conducted on various other sand and binder systems as well as on different specimen thicknesses.

关键词： chemically bonded sand permeability test thermal distortion test loss on ignition

A data-driven health indicator extraction method for aircraft air conditioning system health monitoring

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Chinese Journal of Aeronautics 2019年第2期32卷 409-416页

作者： Jianzhong SUN Chaoyi LI Cui LIU Ziwei GONG Ronghui WANG department of Civil Aviation Nanjing University of Aeronautics and Astronautics maintenance Engineering department Xiamen Airlines

Prognostics and Health management(PHM) has become a very important tool in modern commercial aircraft. Considering limited built-in sensing devices on the legacy aircraft model,one of the challenges for airborne system health monitoring is to find an appropriate health indicator that is highly related to the actual degradation state of the system. This paper proposed a novel health indicator extraction method based on the available sensor parameters for the health monitoring of Air Conditioning system(ACS) of a legacy commercial aircraft model. Firstly, a specific Airplane Condition Monitoring system(ACMS) report for ACS health monitoring is defined. Then a non-parametric modeling technique is adopted to calculate the health indicator based on the raw ACMS report data. The proposed method is validated on a single-aisle commercial aircraft widely used for short and medium-haul routes, using more than 6000 ACMS reports collected from a fleet of aircraft during one year. The case study result shows that the proposed health indicator can effectively characterize the degradation state of the ACS, which can provide valuable information for proactive maintenance plan in advance.

关键词： Air conditioning system Aircraft health monitoring Airplane condition monitoring system Health indicator Prognostics and health management

On finite-time stability and stabilization of nonlinear port-controlled Hamiltonian systems

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Science China(Information Sciences) 2013年第10期56卷 251-264页

作者： WANG YuZhen FENG Gang School of Control Science and Engineering Shandong University department of manufacturing Engineering and Engineering management City University of Hong Kong

The finite-time stability and stabilization of nonlinear port-controlled Hamiltonian(PCH)systems are investigated in this paper,and a number of new results are ***,by exploiting the Hamiltonian structural properties,a proper form of the Hamiltonian function is obtained,based on which a finite-time stability criterion is then presented for a class of Hamiltonian ***,using the obtained stability criterion and the so-called"energy shaping plus damping injection"technique,the continuous finite-time stabilization problem is studied for the PCH system,and several global stabilization results are ***,the continuous robust finite-time stabilization of the PCH system with external disturbances is investigated,and two results on designing global robust finite-time stabilizers are *** of several examples with numerical simulations shows that the control design approach developed in this paper works very well.

关键词： PCH system finite-time stability finite-time stabilization robust stabilization

ESTIMATING CROSS-TRAINING CALL CENTER CAPACITY THROUGH SIMULATION

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Journal of systems Science and systems Engineering 2016年第4期25卷 448-468页

作者： David A. Munoz Nathaniel D. Bastian department of Industrial and manufacturing Engineering The Pennsylvania State University

Call centers have grown world-wide during the past decade. One of the most important aspects considered by call center managers is the optimization of its operators, which implies covering the highly variable demand and f＇mding an efficient way to assign people to certain shifts in order to achieve a desirable service level and abandonment rate. Another challenge is determining which system setup is appropriate for the specific call center. Should we have a single-skill call center or multi-skill call center？ If we do have the latter, how many multi-skill agents should we have on staff？. In this case study, we generate and analyze discrete-event systems simulation-optimization models to test the behavior of a real-world call center under the actual configuration and under different levels of cross-training. The model results help call center managers by： 1） determining the optimal number of operators needed for different staff configtmations in order to achieve the targets for service level and abandonment; 2） providing information about the trade-off between the key measurements in the call center; and 3） providing useful information about the number of operators needed and used for each hour of operation to estimate the number of four-hour shifts required to achieve the performance targets. Our experimental f＇mdings from this case study suggest that a bi-skill call center is economically better in the long-rtm compared to a full-skill or single-skill call center. This case study augments the call center body of knowledge by providing additional managerial insights for the operations management community.

关键词： Call centers cross-training discrete-event systems simulation simulation optimization service operations service systems

Modeling of the resilient supply chain system from a perspective of production design changes

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Frontiers of Engineering management 2023年第1期10卷 96-106页

作者： Shuangshuang ZHANG Hongfeng WANG Guo LI Junwei WANG College of Information Science and Engineering Northeastern UniversityShenyang 110819China School of management and Economics Beijing Institute of TechnologyBeijing 100081China department of Industrial and manufacturing system Engineering The University of Hong KongHong KongChina

Building an effective resilient supply chain system (RSCS) is critical and necessary to reduce the risk of supply chain disruptions in unexpected scenarios such as COVID-19 pandemic and trade wars. To overcome the impact of insufficient raw material supply on the supply chain in mass disruption scenarios, this study proposes a novel RSCS considering product design changes (PDC). An RSCS domain model is first developed from the perspective of PDC based on a general conceptual framework, i.e., function-context-behavior-principle-state-structure (FCBPSS), which can portray complex systems under unpredictable situations. Specifically, the interaction among the structure, state and behavior of the infrastructure system and substance system is captured, and then a quantitative analysis of the change impact process is presented to evaluate the resilience of both the product and supply chain. Next, a case study is conducted to demonstrate the PDC strategy and to validate the feasibility and effectiveness of the RSCS domain model. The results show that the restructured RSCS based on the proposed strategy and model can remedy the huge losses caused by the unavailability of raw materials.

关键词： resilient supply chain supply chain disruption domain modeling product design changes

Active label-denoising algorithm based on broad learning for annotation of machine health status

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Science China(Technological Sciences) 2022年第9期65卷 2089-2104页

作者： LIU GuoKai SHEN WeiMing GAO Liang KUSIAK Andrew State Key Laboratory of Digital manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China department of Industrial and system Engineering The University of IowaSeamans CenterIowa CityIA 52242USA

Deep learning has led to tremendous success in machine maintenance and fault ***,this success is predicated on the correctly annotated *** in large industrial datasets can be noisy and thus degrade the performance of fault diagnosis *** emerging concept of broad learning shows the potential to address the label noise *** with existing deep learning algorithms,broad learning has a simple architecture and high training *** active label denoising algorithm based on broad learning(ALDBL)is ***,ALDBL captures the embedded representation from the time-frequency features by a recurrent memory ***,it augments wide features with a sparse autoencoder and projects the sparse features into an orthogonal space.A proposed corrector then iteratively changes the weights of source examples during the training and corrects the labels by using a label adaptation ***,ALDBL finetunes the model parameters with actively sampled target data with reliable pseudo *** performance of ALDBL is validated with three benchmark datasets,including 30 label denoising *** results demonstrate the effectiveness and advantages of the proposed algorithm over the other label denoising algorithms.

关键词： data annotation broad learning deep learning domain adaptation fault diagnosis noisy label

Control-oriented modeling of a high-aspect-ratio flying wing with coupled flight dynamics

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Chinese Journal of Aeronautics 2023年第4期36卷 409-422页

作者： Cong NIU Xiutian YAN Boyi CHEN department of Design Manufacturing&Engineering ManagementUniversity of StrathclydeGlasgow G11XQUK College of Astronautics Nanjing University of Aeronautics and AstronauticsNanjing 210016China

The flight-structural dynamics of a high-aspect-ratio wing challenge the flight control *** paper develops a reduced model of coupled dynamics with stability *** structural dynamics are formulated with dihedrals,and the central loads drive the *** control-oriented model with essential coupled dynamics is *** sensitivity anal-ysis and input–output pairing are performed to identify the control ***,an example of flight control design is provided to discuss the necessity of considering structural dynamics in controller *** coupled flight dynamics provide a system-theoretic approach for sta-bility and facilitate model-based control *** results reveal the characteristics of flight-structural coupled dynamics and demonstrate that the influence of flexible modes should be considered in control design,especially in lateral dynamics.

关键词： Flexible couplings Flexible wings Flight control systems Flight dynamics Sensitivity analysis

KNOWLEDGE DISTANCE IN INFORMATION systemS

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Journal of systems Science and systems Engineering 2007年第4期16卷 434-449页

作者： Yuhua QIAN Jiye LIANG Chuangyin DANG Feng WANG Wei XU School of Computer & Information Technology Shanxi University Taiyuan 030006 China department of manufacturing Engineering and Engineering management City University of Hong Kong Hong Kong School of management Graduate University of Chinese Academy of Sciences Chinese Academy of SciencesBeifing 100080 China

In this paper, we first introduce the concepts of knowledge closeness and knowledge distance for measuring the sameness and the difference among knowledge in an information system, respectively. The relationship between these two concepts is a strictly mutual complement relation. We then investigaie some important properties of knowledge distance and perform experimental analyses on two public data sets, which show the presented measure appears to be well suited to characterize the nature of knowledge in an information system. Finally, we establish the relationship between the knowledge distance and knowledge granulation, which shows that two variants of the knowledge distance can also be used to construct the knowledge granulation. These results will be helpful for studying uncertainty in information systems.

关键词： Information systems knowledge knowledge distance knowledge granulation

A review of the effects of forest fire on soil properties

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Journal of Forestry Research 2022年第5期33卷 1419-1441页

作者： Alex Amerh Agbeshie Simon Abugre Thomas Atta-Darkwa Richard Awuah department of Environmental management University of Energy and Natural Resources(UENR)SunyaniGhana department of Forest Science University of Energy and Natural Resources(UENR)SunyaniGhana department of Mechanical and manufacturing Engineering University of Energy and Natural Resources(UENR)SunyaniGhana

Forest fires are key ecosystem modifiers affecting the biological,chemical,and physical attributes of forest *** extent of soil disturbance by fire is largely dependent on fire intensity,duration and recurrence,fuel load,and soil *** impact on soil properties is intricate,yielding different results based on these *** paper reviews research investigating the effects of wildfire and prescribed fire on the biological and physico-chemical attributes of forest soils and provides a summary of current knowledge associated with the benefits and disadvantages of such ***-intensity fires with ash deposition on soil surfaces cause changes in soil chemistry,including increase in available nutrients and *** intensity fires are noted for the complete combustion of organic matter and result in severe negative impacts on forest *** intensity fires result in nutrient volatilization,the break down in soil aggregate stability,an increase soil bulk density,an increase in the hydrophobicity of soil particles leading to decreased water infiltration with increased erosion and destroy soil *** soil heating(> 120℃) from high-intensity forest fires is detrimental to the soil ecosystem,especially its physical and biological *** this regard,the use of prescribed burning as a management tool to reduce the fuel load is highly recommended due to its low intensity and limited soil ***,the use of prescribed fires to manage fuel loads is critically needed in the light of current global warming as it will help prevent increased wildfire *** review provides information on the impact of forest fires on soil properties,a key feature in the maintenance of healthy *** addition,the review should prompt comprehensive soil and forest management regimes to limit soil disturbance and restore fire-disturbed soil ecosystems.

关键词： Forest fires Low-severity fire Mineralization Soil available nutrients Soil organic matter Volatilization