Technical University of Berlin

About: Technical University of Berlin is a education organization based out in Berlin, Germany. It is known for research contribution in the topics: Laser & Catalysis. The organization has 27292 authors who have published 59342 publications receiving 1414623 citations. The organization is also known as: Technische Universität Berlin & TU Berlin.

A Review of Theory in Family Business Research: The Implications for Corporate Governance

Abstract: In recent years, increasing scholarly attention has been directed toward the field of family business research. Based on an exhaustive sample of 235 publications, this article provides a comprehensive review and a critical assessment of the theoretical underpinnings and corporate governance issues in family business research. Three predominant theoretical perspectives, namely principal–agent theory, stewardship theory and the resource-based view of the firm, have emerged and provide empirical evidence that family businesses significantly differ from non-family firms in important dimensions such as agency costs, competitive advantages or corporate governance structure. On their own, none of the aforementioned perspectives succeeds in addressing all complexities associated with family businesses and their corporate governance. Accordingly, joint approaches combining different theoretical frameworks can help to improve understanding of the family business. The article concludes by discussing possible directions for future research that might further contribute to building a comprehensive theory of the family business and its corporate governance.

Efficient Supercapacitor Energy Storage Using Conjugated Microporous Polymer Networks Synthesized from Buchwald–Hartwig Coupling

Abstract: Supercapacitors have received increasing interest as energy storage devices due to their rapid charge-discharge rates, high power densities, and high durability. In this work, novel conjugated microporous polymer (CMP) networks are presented for supercapacitor energy storage, namely 3D polyaminoanthraquinone (PAQ) networks synthesized via Buchwald-Hartwig coupling between 2,6-diaminoanthraquinone and aryl bromides. PAQs exhibit surface areas up to 600 m2 g-1 , good dispersibility in polar solvents, and can be processed to flexible electrodes. The PAQs exhibit a three-electrode specific capacitance of 576 F g-1 in 0.5 m H2 SO4 at a current of 1 A g-1 retaining 80-85% capacitances and nearly 100% Coulombic efficiencies (95-98%) upon 6000 cycles at a current density of 2 A g-1 . Asymmetric two-electrode supercapacitors assembled by PAQs show a capacitance of 168 F g-1 of total electrode materials, an energy density of 60 Wh kg-1 at a power density of 1300 W kg-1 , and a wide working potential window (0-1.6 V). The asymmetric supercapacitors show Coulombic efficiencies up to 97% and can retain 95.5% of initial capacitance undergo 2000 cycles. This work thus presents novel promising CMP networks for charge energy storage.

Electric Vehicle Battery Technologies

Abstract: This chapter aims at bridging the gap between chemistry scientists and electrical engineers on electric vehicle (EV) batteries. The power and energy of electric propulsion are first reviewed in Sect. 2.2. Commonly used terms to describe battery performance and characterization are then introduced in Sect. 2.3, followed by the review of various battery charging methods and EV charging schemes in Sect. 2.4. The fundamentals of EV battery technologies are addressed in Sect. 2.5. Two currently most common EV battery technologies, namely, nickel metal hydride (NiMH) and lithium-ion (Li-ion), are covered. It is targeted for giving power engineers a basic understanding of battery chemistry. The EV battery modeling is introduced in Sect. 2.6. It is important for power engineers to appreciate the fundamentals of battery chemistry and battery modeling and use it for power electronic interfacing converter design, battery management, and system level studies. Section 2.7 covers the topic on battery characterization including battery model parameter estimation, state of charge (SOC), and state of health (SOH) estimation. The battery aggregation for power grid applications is discussed in Sect. 2.8. The concept of virtual power plant (VPP) for battery aggregation is introduced to support EV’s participation in power markets.

Construction of Compactly Supported Shearlet Frames

Abstract: Shearlet tight frames have been extensively studied in recent years due to their optimal approximation properties of cartoon-like images and their unified treatment of the continuum and digital settings. However, these studies only concerned shearlet tight frames generated by a band-limited shearlet, whereas for practical purposes compact support in spatial domain is crucial. In this paper, we focus on cone-adapted shearlet systems that—accounting for stability questions—are associated with a general irregular set of parameters. We first derive sufficient conditions for such cone-adapted irregular shearlet systems to form a frame and provide explicit estimates for their frame bounds. Secondly, exploring these results and using specifically designed wavelet scaling functions and filters, we construct a family of cone-adapted shearlet frames consisting of compactly supported shearlets. For this family, we derive estimates for the ratio of their frame bounds and prove that they provide optimally sparse approximations of cartoon-like images. Finally, we discuss an implementation strategy for the shearlet transform based on compactly supported shearlets. We further show that an optimally sparse N-term approximation of an M×M cartoon-like image can be derived with asymptotic computational cost O(M 2(1+τ)) for some positive constant τ depending on M and N.