捶石入纸:拓本生产与流通中的拓工——以晚清缪荃孙及其拓工为中心

拓本是金石学的中心,拓工是拓本生产和传播过程中的关键人物。晚清著名金石学家缪荃孙格外重视拓工,他与很多拓工保持密切交往,其中包括李云从、聂明山、黄士林、沙士瓒、富华阁碑贾小王等人。晚清金石学家与拓工之间的互动,塑造了拓本生产与流通的方式及其特点,晚清拓工的身份地位及其在拓本生产流通中的作用也因而得以突显。

吴大澂和他的拓工

从宋代开始,拓片就成为金石学的重要载体。清代中期以后,金石收藏和研究的品类扩大,对金石拓本的需求也日益增加。吴大澂不但本人会传拓,而且培训拓工,派遣他们访碑拓碑。因此,拓工在晚清金石学发展中所扮演的角色,就成为一个值得关注的学术话题。

以路带危改实现区域经济更快发展

1994年以来,南开区按照天津市委、市政府提出的“用五至七年时间基本完成市区成片危陋平房改造”的战略部署和要求,坚持“一切为了人民,一切依靠人民”的基本工作思路,结合本区实际,以道路拓宽改造为契机,重点突破难点大片地区的改造,并取得了令人瞩目的成绩.1994年至1997年上半年,全区累计实施危改建设项目113个,拆除危陋平房90多万平方米.新建住宅开工300多万平方米,竣工210多万平方米,还迁安置居民42,043户,进一步提高了城市建设和管理水平,带动了区域经济和社会事业的发展.南开区危改拆迁安置工作的主要做法和体会是:

A Realization Method for Transforming a Topology Optimization Design into Additive Manufacturing Structures

Topology optimization is a powerful design approach that is used to determine the optimal topology in order to obtain the desired functional performance. It has been widely used to improve structural performance in engineering fields such as in the aerospace and automobile industries. However, some gaps still exist between topology optimization and engineering application, which significantly hinder the applica- tion of topology optimization. One of these gaps is how to interpret topology results, especially those obtained using the density framework, into parametric computer-aided design （CAD） models that are ready for subsequent shape optimization and manufacturing. In this paper, a new method for interpreting topology optimization results into stereolithography （STL） models and parametric CAD models is pro- posed. First, we extract the skeleton of the topology optimization result in order to ensure shape preser- vation and use a filtering method to ensure characteristics preservation. After this process, the distribution of the nodes in the boundary of the topology optimization result is denser, which will benefit the subsequent curve fitting. Using the curvature and the derivative of curvature of the uniform B-spline curve, an adaptive B-spline fitting method is proposed in order to obtain a parametric CAD model with the fewest control points meeting the requirement of the fitting error. A case study is presented to pro- vide a detailed description of the proposed method, and two more examples are shown to demonstrate the validity and versatility of the proposed method.

CLOSE-LOOP DESIGN OF PULSE POWER SUPPLY FOR ELECTRICAL DISCHARGE MACHINING

The dynamic performance and the stability are essential for a system. A new circuit topology used for electrical discharge machining (EDM) power and made up of complex-pulse (voltage-pulse and current-pulse) is presented. The large-signal model of it is also derived. Based on the comprehensive analysis of the system model, the compensator is designed to make the system match better and to improve its dynamic performance and the stability under perturbations. Finally, the design methods and the analysis are verified by simulation and experimental results.

A New Extension Theory-based Production Operation Method in Industrial Process

To explore the problems of dynamic change in production demand and operating contradiction in production process, a new extension theory-based production operation method is proposed. The core is the demand requisition, contradiction resolution and operation classification. For the demand requisition, the deep and comprehensive demand elements are collected by the conjugating analysis. For the contradiction resolution, the conflict between the demand and operating elements are solved by the extension reasoning, extension transformation and consistency judgment. For the operating classification, the operating importance among the operating elements is calculated by the extension clustering so as to guide the production operation and ensure the production safety. Through the actual application in the cascade reaction process of high-density polyethylene (HDPE) of a chemical plant, cases study and comparison show that the proposed extension theory-based production operation method is significantly better than the traditional experience-based operation method in actual production process, which exploits a new way to the research on the production operating methods for industrial process.

AN ALGORITHM FOR END-TO-END PERFORMANCE ANALYSIS OF NETWORK BASED ON TRAFFIC ENGINEERING

Based on traffic engineering, the network topology is described with network graph. An algorithm for the derivation of data communication capability in network links and the analysis of connectivity performance between node pairs is given through standardized transformation of the original descriptive matrix for the link performance, and resolution of transitive closure for adjacent-incident matrix of network in view of randomness of network events, which provides a feasible way for analysis and improvement of network performance.

Alternate solutions for mine ventilation network to keep a preassigned fixed quantity in a working place

In underground constructions, a good ventilation design not only delivers fresh air to establish good working environment, but also provides a scientific and reliable basis to prevent disasters. In emergency cases, unexpected closure of the main airways may occur, providing the workers with alternative airways is substantial. This is important not only to sustain personnel lives, but also to prevent the mine ventilation system from damage. In this research, alternate solutions were introduced in case of failure in the underground construction to keep a pre-assigned fixed quantity in a working place for mine ventilation network. Eight different collapse scenarios were proposed to study their effect on the air quantity distribution among the branches in the ventilation circuit. From these scenarios, it is found that providing a sufficient air quantity in the working places could be achieved through modification of the network topology and adjusting the values of the regulators pressure. It is also indicated that the distance between the collapse and working places has a great effect on the amount of air delivered to it. A reduction in the power consumption could be done by re-arrange the installed regulators and decreasing the number of nodes and branches inside the network. A relationship representing the effect of changing the network topology on the total network power consumption was deduced through regression analysis. It is found that the total network power is quadratic dependent on the number of regulators and number of branches while it is directly dependent on the regulator power.

社会史视角下的清代金石学研究

清代金石学的繁荣固然与学者的访碑、交游、鉴赏息息相关,但从微观角度或消极方面探索这种繁荣背后的几股力量更能深入清代朴学的内部。政治上,不少文人士子将与官场权贵鉴赏、交流金石碑拓视为亲近权贵和获得升迁的工具;经济上,拓工为官场富豪捶拓不但能够获得经济上的满足,在政治上也有便利;文化上,部分仕途无望的文人将金石研究视为声名千古、永继不朽的见证,不断著书立说。金石学作为清代学术的重要组成部分,连接着经学、史学、文字学等其他学科,金石学家亦不专精一门。从社会史的角度可以看到学问之互通、学者之交游,这些消极因素往往是清代金石学发展的促进力量。

Majorana zero mode in the vortex of an artificial topological superconductor

Majorana fermion （MF）, an exotic particle that is identical to its own antiparticle, was recently found in solid matter as a quasiparticle excitation, the Majorana zero mode （MZM）, in the vortex of an artificial topological superconductor （TSC）. This artificial TSC, first proposed by Fu and Kane in 2008, is a heterostructure made of a topological insulator BiETe3 and an s-wave superconductor NbSe2. This paper will briefly review the experimental progresses based on the Bi2Te3/NbSe2 heterostructure. All evidences are self-consistent and reveal that the MZM exists in the center of vortex. Those experimental results are also supported by theory. This finding is a milestone in the research ofMajorana fermions in solid state physics and a starting point of MZM＇s application in topological quantum computation.

Distributed Consensus-Based K-Means Algorithm in Switching Multi-Agent Networks

This paper discusses a distributed design for clustering based on the K-means algorithm in a switching multi-agent network, for the case when data are decentralized stored and unavailable to all agents. The authors propose a consensus-based algorithm in distributed case, that is, the double- clock consensus-based K-means algorithm （DCKA）. With mild connectivity conditions, the authors show convergence of DCKA to guarantee a distributed solution to the clustering problem, even though the network topology is time-varying. Moreover, the authors provide experimental results on vari- ous clustering datasets to illustrate the effectiveness of the fully distributed algorithm DCKA, whose performance may be better than that of the centralized K-means algorithm.

Exploring link generation in a temporal evolution network for human mobility

The prevalence of mobile devices has spurred human mobility to be applied in mobile networking and communications by using network science, in which the temporal evolution of a network topology is of great importance for protocol design and performance analysis. This paper focuses on link generation in a temporal evolution network. Based on observations revealing the strong correlation between the connection patterns of different time periods, a link generation potential based on historical connections is proposed in this paper, aiming to provide a method for making topological predictions with less randomness. Using MIT Reality dataset, an evaluation of the accuracy of the proposed method was conducted. The experimental results demonstrate the proposal's adequacy in terms of its accuracy.

Algorithms for seismic topology optimization of water distribution network

As an essential lifeline engineering system,water distribution network should provide enough water to maintain people's life after earthquake in addition to working under daily operation.However,the design of water distribution network usually ignores the influence of earthquake,resulting in water stoppage in large area during many recent strong earthquakes.This study introduced a seismic design approach of water distribution network,i.e.,topology optimization design.With network topology as the optimization goal and seismic reliability as the constraint,a topology optimization model for designing water distribution network under earthquake is established.Meanwhile,two element investment importance indexes,a pipeline investment importance index and a diameter investment importance index,are introduced to evaluate the importance of pipelines in water distribution network.Then,four combinational optimization algorithms,a genetic algorithm,a simulated annealing genetic algorithm,an ant colony algorithm and a particle swarm algorithm,are introduced to solve this optimization model.Moreover,these optimization algorithms are used to optimize a network with 19 nodes and 27 pipelines.The optimization results of these algorithms are compared with each other.