IFAC Proceedings Volumes最新文献

英文中文

Computing Instantaneous Throughput For Spatially Constrained Aiming Tasks 计算空间受限瞄准任务的瞬时吞吐量

IFAC Proceedings Volumes

Pub Date : 2014-01-01 DOI: 10.3182/20140824-6-ZA-1003.01696

J. N. Shelton, G. Chiu

Abstract Motor throughput is a standard measure of how rapidly information can be transmitted through an input device (such as a mouse or wand) by a human user carrying out point-to-point movement (also known as a Fitts' task.) As low-cost motion tracking systems become more prevalent, engineers are presented with increasing opportunities to control operations using hand gestures. However, accurate analysis of motor throughput in such cases may be difficult, as muscle tremors may prevent midair motions from coming to an absolute stop, and visual obstructions may prevent endpoint data from being reliably captured. A lack of accurate temporal and spatial endpoint information precludes any determination of motor throughput. Inspired by Fitts' information channel model, we derive a measure of instantaneous motor throughput. Observation of this instantaneous measure demonstrates how the traditional measure of information bandwidth, Fitts' motor throughput, emerges during the course of an aimed movement. Further, an experimental study demonstrates that instantaneous throughput (ITP) profiles exhibit a common shape when plotted against normalized distance. We select the moment of peak variance to be the most convenient landmark along the ITP trajectory for computing an overall throughput value, and demonstrate that this new method compares favorably with traditional throughput measures.

运动吞吐量是衡量人类用户通过输入设备(如鼠标或魔杖)进行点对点运动(也称为Fitts任务)的信息传输速度的标准度量。随着低成本运动跟踪系统变得越来越普遍，工程师们有越来越多的机会使用手势来控制操作。然而，在这种情况下，准确分析运动吞吐量可能很困难，因为肌肉震颤可能会阻止半空中运动完全停止，并且视觉障碍可能会阻止可靠地捕获端点数据。缺乏准确的时间和空间端点信息妨碍了对电机吞吐量的任何确定。受Fitts信息通道模型的启发，我们得出了电机瞬时吞吐量的度量。对这种瞬时测量的观察表明，传统的信息带宽测量，即菲茨运动吞吐量，是如何在目标运动过程中出现的。此外，一项实验研究表明，瞬时吞吐量(ITP)曲线在与归一化距离绘制时呈现出共同的形状。我们选择峰值方差时刻作为沿ITP轨迹计算总吞吐量值的最方便的标志，并证明这种新方法与传统的吞吐量度量方法相比具有优势。

{"title":"Computing Instantaneous Throughput For Spatially Constrained Aiming Tasks","authors":"J. N. Shelton, G. Chiu","doi":"10.3182/20140824-6-ZA-1003.01696","DOIUrl":"https://doi.org/10.3182/20140824-6-ZA-1003.01696","url":null,"abstract":"Abstract Motor throughput is a standard measure of how rapidly information can be transmitted through an input device (such as a mouse or wand) by a human user carrying out point-to-point movement (also known as a Fitts' task.) As low-cost motion tracking systems become more prevalent, engineers are presented with increasing opportunities to control operations using hand gestures. However, accurate analysis of motor throughput in such cases may be difficult, as muscle tremors may prevent midair motions from coming to an absolute stop, and visual obstructions may prevent endpoint data from being reliably captured. A lack of accurate temporal and spatial endpoint information precludes any determination of motor throughput. Inspired by Fitts' information channel model, we derive a measure of instantaneous motor throughput. Observation of this instantaneous measure demonstrates how the traditional measure of information bandwidth, Fitts' motor throughput, emerges during the course of an aimed movement. Further, an experimental study demonstrates that instantaneous throughput (ITP) profiles exhibit a common shape when plotted against normalized distance. We select the moment of peak variance to be the most convenient landmark along the ITP trajectory for computing an overall throughput value, and demonstrate that this new method compares favorably with traditional throughput measures.","PeriodicalId":13260,"journal":{"name":"IFAC Proceedings Volumes","volume":"18 1","pages":"7208-7213"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74382998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 1

From Linear to Nonlinear Model Predictive Control of a Building 从线性模型到非线性模型的建筑物预测控制

IFAC Proceedings Volumes

Pub Date : 2014-01-01 DOI: 10.3182/20140824-6-ZA-1003.02783

Matej Pčolka , Eva Žáčeková , Rush Robinett , Sergej Čelikovský , Michael Sebek

In the building climate control area, the linear model predictive control (LMPC)—nowadays considered a mature technique—benefits from the fact that the resulting optimization task is convex (thus easily and quickly solvable). On the other hand, while nonlinear model predictive control (NMPC) using a more detailed nonlinear model of a building takes advantage of its more accurate predictions and the fact that it attacks the optimization task more directly, it requires more involved ways of solving the non-convex optimization problem. In this paper, the gap between LMPC and NMPC is bridged by introducing several variants of linear time-varying model predictive controller (LTVMPC). Making use of linear time-varying model of the controlled building, LTVMPC obtains predictions which are closer to reality than those of linear time invariant model while still keeping the optimization task convex and less computationally demanding than in the case of NMPC. The concept of LTVMPC is verified on a set of numerical experiments performed using a high fidelity model created in a building simulation environment and compared to the previously mentioned alternatives (LMPC and NMPC) looking at both the control performance and the computational requirements.

摘要:在建筑气候控制领域，线性模型预测控制(LMPC)是一种成熟的技术，其优化任务是凸的(因此易于快速求解)。另一方面，虽然非线性模型预测控制(NMPC)使用更详细的建筑物非线性模型，利用其更准确的预测和更直接地攻击优化任务的事实，但它需要更复杂的方法来解决非凸优化问题。本文通过引入线性时变模型预测控制器(LTVMPC)的几个变体，弥补了LMPC和NMPC之间的差距。LTVMPC利用被控建筑的线性时变模型，在保证优化任务的凸性和减少计算量的前提下，获得了比线性时不变模型更接近实际的预测结果。LTVMPC的概念通过在建筑仿真环境中创建的高保真模型进行的一组数值实验进行了验证，并与前面提到的替代方案(LMPC和NMPC)进行了比较，同时考虑了控制性能和计算需求。

{"title":"From Linear to Nonlinear Model Predictive Control of a Building","authors":"Matej Pčolka , Eva Žáčeková , Rush Robinett , Sergej Čelikovský , Michael Sebek","doi":"10.3182/20140824-6-ZA-1003.02783","DOIUrl":"10.3182/20140824-6-ZA-1003.02783","url":null,"abstract":"<div><p>In the building climate control area, the linear model predictive control (LMPC)—nowadays considered a mature technique—benefits from the fact that the resulting optimization task is convex (thus easily and quickly solvable). On the other hand, while nonlinear model predictive control (NMPC) using a more detailed nonlinear model of a building takes advantage of its more accurate predictions and the fact that it attacks the optimization task more directly, it requires more involved ways of solving the non-convex optimization problem. In this paper, the gap between LMPC and NMPC is bridged by introducing several variants of linear time-varying model predictive controller (LTVMPC). Making use of linear time-varying model of the controlled building, LTVMPC obtains predictions which are closer to reality than those of linear time invariant model while still keeping the optimization task convex and less computationally demanding than in the case of NMPC. The concept of LTVMPC is verified on a set of numerical experiments performed using a high fidelity model created in a building simulation environment and compared to the previously mentioned alternatives (LMPC and NMPC) looking at both the control performance and the computational requirements.</p></div>","PeriodicalId":13260,"journal":{"name":"IFAC Proceedings Volumes","volume":"47 3","pages":"Pages 587-592"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3182/20140824-6-ZA-1003.02783","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74482852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 6

Structured optimisation dynamics for robust triple mode predictive control 鲁棒三模预测控制的结构优化动力学

IFAC Proceedings Volumes

Pub Date : 2014-01-01 DOI: 10.3182/20140824-6-ZA-1003.00903

B. Khan, J. Rossiter

Abstract This paper makes contribution in the area of model based predictive control (MPC) and in particular examines to what extent structured optimisation dynamics can improve regions of attraction, performance and computational burden in the robust case. This paper focuses on the use of structured prediction dynamics within a robust triple mode MPC context and demonstrates that these can simplify the design significantly while retaining good robust feasibility regions and performance. The improvements, with respect to existing algorithms are demonstrated by numerical examples using statistical analysis.

本文在基于模型的预测控制(MPC)领域做出了贡献，特别是研究了在鲁棒情况下，结构化优化动力学在多大程度上可以改善吸引力、性能和计算负担区域。本文着重于在鲁棒三模MPC环境中使用结构化预测动力学，并证明这些可以显着简化设计，同时保持良好的鲁棒可行性区域和性能。通过统计分析的数值算例证明了对现有算法的改进。

引用次数: 0

Recognition of Human Body Movements Trajectory Based on the Three-Dimensional Depth Data 基于三维深度数据的人体运动轨迹识别

IFAC Proceedings Volumes

Pub Date : 2014-01-01 DOI: 10.3182/20140824-6-ZA-1003.00532

Zheng Chang, Qing Shen, X. Ban, Jing Guo

Abstract based on the traditional machine vision recognition technology about human body movement trajectory, the paper finds out the shortcomings of the traditional recognition technology. By combining the three - dimensional depth data, the three-dimensional motion history image and the invariant moments of the three - dimensional motion history image computed as the eigenvector of body movements, the paper applies the method to the machine vision of the human body movements trajectory. In detail, the paper describes the algorithm and realization scheme of the human body movements trajectory recognition based on the three-dimensional depth data. Finally, comparing with the results of the recognition experiment, we verify that the method of human body movement trajectory recognition technology based on the three-dimensional data has a more accurate recognition rate and a better robustness.

摘要基于传统的机器视觉识别技术对人体运动轨迹的识别，找出了传统识别技术的不足。将三维深度数据、三维运动历史图像和计算出的三维运动历史图像的不变矩作为人体运动的特征向量相结合，将该方法应用于人体运动轨迹的机器视觉。详细介绍了基于三维深度数据的人体运动轨迹识别算法和实现方案。最后，通过与识别实验结果的对比，验证了基于三维数据的人体运动轨迹识别技术方法具有更准确的识别率和更好的鲁棒性。

引用次数: 2

Switched model predictive control for networked control systems with time delays and packet disordering 具有时延和包无序的网络控制系统的交换模型预测控制

IFAC Proceedings Volumes

Pub Date : 2014-01-01 DOI: 10.3182/20140824-6-ZA-1003.01116

Andong Liu, Li Yu, Wen-an Zhang

Abstract The switched model predictive control (MPC) strategy is investigated in this paper for a class of networked control systems (NCSs) with time delays and packet disordering. A new model is proposed to describe the NCS with packet disordering. State feedback controllers are considered and the resulting closed-loop NCS is modeled as a discrete-time switched system. By using the average dwell-time approach and switching between different cost functions, sufficient conditions for exponential stability of the NCS and design procedures for the stabilizing controllers are presented. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed method.

摘要针对一类具有时延和包无序的网络控制系统，研究了交换模型预测控制策略。提出了一种新的模型来描述具有包无序的网络控制系统。考虑状态反馈控制器，并将得到的闭环网络控制系统建模为一个离散时间切换系统。利用平均停留时间方法和不同代价函数之间的切换，给出了NCS指数稳定的充分条件和稳定控制器的设计步骤。最后，通过一个算例验证了该方法的有效性。

引用次数: 4

Evaluation of Aggregators for Integration of Large-scale Consumers in Smart Grid 智能电网中大规模用户集成的聚合器评价

IFAC Proceedings Volumes

Pub Date : 2014-01-01 DOI: 10.3182/20140824-6-ZA-1003.00601

Samira Rahnama, S. E. Shafiei, J. Stoustrup, H. Rasmussen, J. Bendtsen

Abstract Utilization of consumers to mitigate the impact of increasing renewable resources on power systems is one of the visions of future smart grids. Flexible consumers are consumers who can change their consumption patterns in such a way as to help the grid to tackle the balancing problem. In previous work, we proposed a hierarchical structure to provide regulating power to the grid by just utilizing the consumption units. The main focus of that work was on designing a centralized controller, a so-called aggregator, which is responsible for aggregating the flexibilities in an optimal way. To accomplish the optimization, the aggregator requires a model which describes the behavior of each consumption unit. These models should be sufficiently simple to be used in the optimization task. However, simple models might not capture all dynamics and features of the real system. In this paper, we will evaluate the proposed setup to understand to what extent the utilization of simplified models can lead to reasonable results. To this end, we will connect the aggregator to a complex and verified model of an actual supermarket refrigeration system which enables us to investigate the closed-loop behavior of the whole set-up.

利用消费者来减轻不断增加的可再生资源对电力系统的影响是未来智能电网的愿景之一。灵活的消费者是指能够改变自己的消费模式，从而帮助电网解决平衡问题的消费者。在之前的工作中，我们提出了一种分层结构，仅利用消费单元向电网提供调节功率。这项工作的主要重点是设计一个集中的控制器，即所谓的聚合器，它负责以最优的方式聚合灵活性。为了完成优化，聚合器需要一个描述每个消费单元行为的模型。这些模型应该足够简单，以便在优化任务中使用。然而，简单的模型可能无法捕获真实系统的所有动态和特征。在本文中，我们将评估所提出的设置，以了解简化模型的使用在多大程度上可以导致合理的结果。为此，我们将把聚合器连接到一个实际超市制冷系统的复杂且经过验证的模型，该模型使我们能够研究整个装置的闭环行为。

{"title":"Evaluation of Aggregators for Integration of Large-scale Consumers in Smart Grid","authors":"Samira Rahnama, S. E. Shafiei, J. Stoustrup, H. Rasmussen, J. Bendtsen","doi":"10.3182/20140824-6-ZA-1003.00601","DOIUrl":"https://doi.org/10.3182/20140824-6-ZA-1003.00601","url":null,"abstract":"Abstract Utilization of consumers to mitigate the impact of increasing renewable resources on power systems is one of the visions of future smart grids. Flexible consumers are consumers who can change their consumption patterns in such a way as to help the grid to tackle the balancing problem. In previous work, we proposed a hierarchical structure to provide regulating power to the grid by just utilizing the consumption units. The main focus of that work was on designing a centralized controller, a so-called aggregator, which is responsible for aggregating the flexibilities in an optimal way. To accomplish the optimization, the aggregator requires a model which describes the behavior of each consumption unit. These models should be sufficiently simple to be used in the optimization task. However, simple models might not capture all dynamics and features of the real system. In this paper, we will evaluate the proposed setup to understand to what extent the utilization of simplified models can lead to reasonable results. To this end, we will connect the aggregator to a complex and verified model of an actual supermarket refrigeration system which enables us to investigate the closed-loop behavior of the whole set-up.","PeriodicalId":13260,"journal":{"name":"IFAC Proceedings Volumes","volume":"7 1","pages":"1879-1885"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75253418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 20

Finite Element Approximation and Input Parameterization for the Optimal Control of Current Profiles in Tokamak Plasmas 托卡马克等离子体电流分布最优控制的有限元逼近和输入参数化

IFAC Proceedings Volumes

Pub Date : 2014-01-01 DOI: 10.3182/20140824-6-ZA-1003.00429

Zhigang Ren, Chao Xu, Qun Lin, R. Loxton, K. Teo, Jian Chu

Abstract In this paper, we consider a simplified dynamic model describing the evolution of the poloidal flux during the ramp-up phase of the tokamak discharge. We first use the Galerkin method to obtain a finite-dimensional model based on the original PDE system. Then, we apply the control parameterization method to obtain an approximate optimal parameter selection problem governed by a lumped parameter system. Computational optimization techniques are subsequently deployed to solve this approximate problem. To validate our approach, we perform numerical simulations using experimental data from the DIII-D tokamak in San Diego, California. The results show that our numerical optimization procedure can generate optimal controls that drive the current profile to within close proximity of the desired profile at the terminal time, thus demonstrating that the Galerkin and control parameterization methods are effective tools for current profile control in tokamak plasmas.

摘要本文考虑了一个简化的动态模型来描述托卡马克放电上升阶段的极流通量演变。我们首先利用伽辽金方法在原PDE系统的基础上得到一个有限维的模型。然后，应用控制参数化方法，得到了一个集总参数系统的近似最优参数选择问题。计算优化技术随后被部署来解决这个近似问题。为了验证我们的方法，我们使用加利福尼亚州圣地亚哥的DIII-D托卡马克的实验数据进行了数值模拟。结果表明，我们的数值优化程序可以产生最优控制，使电流剖面在终端时刻接近所需剖面，从而表明伽辽金和控制参数化方法是托卡马克等离子体电流剖面控制的有效工具。

引用次数: 2

Analysis of scale invariance property applying homogeneity 应用均匀性分析尺度不变性

IFAC Proceedings Volumes

Pub Date : 2014-01-01 DOI: 10.3182/20140824-6-ZA-1003.02370

E. Bernuau, D. Efimov, W. Perruquetti

The problem of scalability of trajectories in homogeneous and locally homogeneous systems is considered. It is shown that the homogeneous systems have scalability property, and locally homogeneous systems possess this property approximately. The issue of closeness of trajectories for the system and its local homogeneous approximation is investigated. The notions of scale invariance and fold change detection are also studied. The results are illustrated by a cascade system analysis.

研究了齐次系统和局部齐次系统中轨迹的可扩展性问题。证明了齐次系统具有可扩展性，局部齐次系统近似地具有可扩展性。研究了系统轨迹的密切性及其局部齐次逼近问题。研究了尺度不变性和折叠变化检测的概念。结果用级联系统分析加以说明。

引用次数: 1

Searching force-closure optimal grasps of articulated 2D objects with n links 搜索具有n个连杆的铰接二维物体的力闭合最佳抓取

IFAC Proceedings Volumes

Pub Date : 2014-01-01 DOI: 10.3182/20140824-6-ZA-1003.01018

Noe Alvarado Tovar, R. Suárez

This paper proposes a method that finds a locally optimal grasp of an articulated 2D object with n links considering frictionless contacts. The surface of each link of the object is represented by a finite set of points, thus it may have any shape. The proposed approach finds, first, an initial force-closure grasp and from it starts an iterative search of a local optimum grasp. The quality measure considered in this work is the largest perturbation wrench that a grasp can resist with independence of the direction of the perturbation. The approach has been implemented and some illustrative examples are included in the article.

本文提出了一种考虑无摩擦接触的n个连杆铰接二维物体的局部最优抓取方法。物体的每一个连杆的表面由一组有限的点表示，因此它可以有任何形状。提出的方法首先找到一个初始力闭合抓点，然后从它开始迭代搜索局部最优抓点。在这项工作中考虑的质量度量是一个抓手可以抵抗的与摄动方向无关的最大摄动扳手。本文已经实现了该方法，并给出了一些说明性示例。

引用次数: 5

Simultaneous State and Fault Estimation for Descriptor Systems using an Augmented PD Observer 基于增广PD观测器的广义系统同步状态和故障估计

IFAC Proceedings Volumes

Pub Date : 2014-01-01 DOI: 10.3182/20140824-6-ZA-1003.01383

F. Shi, R. Patton

Abstract This paper proposes an augmented Proportional plus Derivative (PD) state estimator to achieve simultaneous system state and fault estimation of descriptor systems. Descriptor systems without model uncertainty are initially considered, followed by a discussion of a general situation where the system model is subject to model uncertainty, external disturbance or sensor noise. The H ∞ performance is adopted to improve the estimator robustness subject to disturbance, sensor noise or model uncertainty. The estimator gains are obtained via an LMI approach. An example is studied to show the usefulness and effectiveness of the proposed approach.

提出了一种增广比例加导数(PD)状态估计器，用于同时估计广义系统的状态和故障。首先考虑无模型不确定性的广义系统，然后讨论系统模型受模型不确定性、外部干扰或传感器噪声影响的一般情况。采用H∞性能来提高估计器对干扰、传感器噪声或模型不确定性的鲁棒性。估计器增益是通过LMI方法获得的。算例表明了该方法的有效性和实用性。

引用次数: 23

首页上一页

下一页尾页

类型

全部化学•材料生命科学医学物理工程技术环境•农林材料科学地球科学法学管理学化学环境科学与生态学计算机科学教育学经济学农林科学人文科学生物学数学物理与天体物理心理学综合性期刊其他工业工程理学历史学农学文学信息工程

数据库

全部 ACS Publications Elsevier ieeexplore Springer The Royal Society of Chemistry Wiley

期刊

IFAC Proceedings Volumes

全部 Acc. Chem. Res. ACS Applied Bio Materials ACS Appl. Electron. Mater. ACS Appl. Energy Mater. ACS Appl. Mater. Interfaces ACS Appl. Nano Mater. ACS Appl. Polym. Mater. ACS BIOMATER-SCI ENG ACS Catal. ACS Cent. Sci. ACS Chem. Biol. ACS Chemical Health & Safety ACS Chem. Neurosci. ACS Comb. Sci. ACS Earth Space Chem. ACS Energy Lett. ACS Infect. Dis. ACS Macro Lett. ACS Mater. Lett. ACS Med. Chem. Lett. ACS Nano ACS Omega ACS Photonics ACS Sens. ACS Sustainable Chem. Eng. ACS Synth. Biol. Anal. Chem. BIOCHEMISTRY-US Bioconjugate Chem. BIOMACROMOLECULES Chem. Res. Toxicol. Chem. Rev. Chem. Mater. CRYST GROWTH DES ENERG FUEL Environ. Sci. Technol. Environ. Sci. Technol. Lett. Eur. J. Inorg. Chem. IND ENG CHEM RES Inorg. Chem. J. Agric. Food. Chem. J. Chem. Eng. Data J. Chem. Educ. J. Chem. Inf. Model. J. Chem. Theory Comput. J. Med. Chem. J. Nat. Prod. J PROTEOME RES J. Am. Chem. Soc. LANGMUIR MACROMOLECULES Mol. Pharmaceutics Nano Lett. Org. Lett. ORG PROCESS RES DEV ORGANOMETALLICS J. Org. Chem. J. Phys. Chem. J. Phys. Chem. A J. Phys. Chem. B J. Phys. Chem. C J. Phys. Chem. Lett. Analyst Anal. Methods Biomater. Sci. Catal. Sci. Technol. Chem. Commun. Chem. Soc. Rev. CHEM EDUC RES PRACT CRYSTENGCOMM Dalton Trans. Energy Environ. Sci. ENVIRON SCI-NANO ENVIRON SCI-PROC IMP ENVIRON SCI-WAT RES Faraday Discuss. Food Funct. Green Chem. Inorg. Chem. Front. Integr. Biol. J. Anal. At. Spectrom. J. Mater. Chem. A J. Mater. Chem. B J. Mater. Chem. C Lab Chip Mater. Chem. Front. Mater. Horiz. MEDCHEMCOMM Metallomics Mol. Biosyst. Mol. Syst. Des. Eng. Nanoscale Nanoscale Horiz. Nat. Prod. Rep. New J. Chem. Org. Biomol. Chem. Org. Chem. Front. PHOTOCH PHOTOBIO SCI PCCP Polym. Chem.

﹀