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Henk van Zeijl

Bio: Henk van Zeijl is an academic researcher from Delft University of Technology. The author has contributed to research in topics: Wafer & Light-emitting diode. The author has an hindex of 10, co-authored 37 publications receiving 405 citations.

Papers
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Journal ArticleDOI
TL;DR: Self-healing concepts will be proposed to further improve LED’s reliability in order to increase reliability of SSL devices, components presenting self-repairing properties could be implemented.

112 citations

Journal ArticleDOI
TL;DR: In this paper, only passive thermal solutions used on LED module will be studied and new thermal interface materials and passive thermal solution applied on electronic equipments are discussed which have high potential to enhance the thermal performance of LED Module.
Abstract: Recently, the high-brightness LEDs have begun to be designed for illumination application. The increased electrical currents used to drive LEDs lead to thermal issues. Thermal management for LED module is a key design parameter as high operation temperature directly affects their maximum light output, quality, reliability and life time. In this review, only passive thermal solutions used on LED module will be studied. Moreover, new thermal interface materials and passive thermal solutions applied on electronic equipments are discussed which have high potential to enhance the thermal performance of LED Module.

64 citations

Journal ArticleDOI
TL;DR: In this article, a thermally conductive composites with a temperature-triggered self-healing response were produced by dispersing boron nitride or graphite particles into two types of polysulphide-based thermoset matrices.
Abstract: Thermally conductive composites with a temperature-triggered self-healing response were produced by dispersing boron nitride or graphite particles into two types of polysulphide-based thermoset matrices. The composites produced exhibit recovery of both cohesion and adhesion properties upon thermally activated healing. Using a mild healing temperature (65°C), the materials show full recovery of their initial adhesive strength during multiple healing cycles. The composites behave differently regarding the cohesion recovery: 20%–100% recovery is achieved depending on the filler type, filler loading and the type of matrix. The thermal conductivity of the composites increases with the amount of filler. Values of 1 and 2 W/m K can be achieved for the boron nitride and graphite-based composite, respectively. The results presented in this work clearly show that multifunctional materials with different functionalities and mechanical self-healing responses can be designed using this strategy.

38 citations

Journal ArticleDOI
TL;DR: The design of a bulk micromachined MEMS device exploiting non-linear buckling behaviour is described, aiming for n∕Hz resolution by maximising mechanical and capacitive sensitivity.
Abstract: Commercially available gravimeters and seismometers can be used for measuring Earth’s acceleration at resolution levels in the order of $${\mathrm{ng}}/\sqrt {\mathrm{Hz}}$$ (where g represents earth’s gravity) but they are typically high-cost and bulky. In this work the design of a bulk micromachined MEMS device exploiting non-linear buckling behaviour is described, aiming for $${\mathrm{ng}}/\sqrt {\mathrm{Hz}}$$ resolution by maximising mechanical and capacitive sensitivity. High mechanical sensitivity is obtained through low structural stiffness. Near-zero stiffness is achieved through geometric design and large deformation into a region where the mechanism is statically balanced or neutrally stable. Moreover, the device has an integrated capacitive comb transducer and makes use of a high-resolution impedance readout ASIC. The sensitivity from displacement to a change in capacitance was maximised within the design and process boundaries given, by making use of a trench isolation technique and exploiting the large-displacement behaviour of the device. The measurement results demonstrate that the resonance frequency can be tuned from 8.7 Hz–18.7 Hz, depending on the process parameters and the tilt of the device. In this system, which combines an integrated capacitive transducer with a sensitivity of 2.55 aF/nm and an impedance readout chip, the theoretically achievable system resolution equals 17.02 $${\mathrm{ng}}/\sqrt {\mathrm{Hz}}$$ . The small size of the device and the use of integrated readout electronics allow for a wide range of practical applications for data collection aimed at the internet of things. A micromechanical system (MEMS) has been developed that allows accurate measurement of acceleration at high-resolution levels. Commercially available gravimeters and seismometers can be used for high-resolution measurement of the earth’s acceleration, but they are typically very expensive and bulky. However, a team headed by Guo Qi Zhang at Delft University of Technology, Netherlands was able to design, simulate, fabricate and test a low-cost MEMS device with an integrated miniaturized high-sensitivity transducer for high-resolution acceleration measurements. The team was able to process and package its device by wirebonding it to a printed circuit board containing an application-specific integrated circuit. The authors believe that their extremely compact, low-power inertial sensor has considerable potential for a wide range of practical applications for data collection with the Internet of things.

33 citations

Journal ArticleDOI
TL;DR: In this article, the results of design, manufacturing and characterization of VLM with integrated molybdenum heaters and temperature sensing are presented for use in CubeSats and PocketQubes.
Abstract: This paper presents the results of design, manufacturing and characterization of Vaporizing Liquid Microthrusters (VLM) with integrated molybdenum heaters and temperature sensing. The thrusters use water as the propellant and are designed for use in CubeSats and PocketQubes. The devices are manufactured using silicon based MEMS (Micro Electro Mechanical Systems) technology and include resistive heaters to vaporize the propellant. The measurements of the heaters’ resistances are used to estimate the temperature in the vaporizing chamber. The manufacturing process is described as well as the characterization of the thrusters’ structural and electrical elements. In total 12 devices with different combinations of heaters and nozzles have been assessed and four of them have been used to demonstrate the successful operation of the thrusters. Results are used to validate the thrusters and show a performance close to the design parameters and comparable to other devices found in the literature.

28 citations


Cited by
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Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

01 Jan 2016
TL;DR: The design of analog cmos integrated circuits is universally compatible with any devices to read and is available in the book collection an online access to it is set as public so you can download it instantly.
Abstract: Thank you for downloading design of analog cmos integrated circuits. Maybe you have knowledge that, people have look hundreds times for their chosen books like this design of analog cmos integrated circuits, but end up in malicious downloads. Rather than enjoying a good book with a cup of coffee in the afternoon, instead they juggled with some harmful virus inside their computer. design of analog cmos integrated circuits is available in our book collection an online access to it is set as public so you can download it instantly. Our digital library spans in multiple countries, allowing you to get the most less latency time to download any of our books like this one. Kindly say, the design of analog cmos integrated circuits is universally compatible with any devices to read.

1,038 citations

Journal ArticleDOI
TL;DR: In this paper, the authors provide an overview of recent progress in developing transparent inorganic glass-ceramics phosphors excitable by blue chip, as an alternative to conventional polymer-based phosphor converter, for construction of high-power white light-emitting diodes.
Abstract: Currently, the major commercial white light-emitting diode is the phosphor converted LED made of blue-emitting chip and Y 3 Al 5 O 12 :Ce 3+ yellow phosphor dispersed in organic silicone. However, the organic binder in high-power device ages easily and turns yellow due to accumulated heat emitted from chip, which adversely affects the device properties such as luminous efficacy and color coordination, and therefore reduces its long-term reliability as well as lifetime. In this mini-review article, we provide an overview of recent progresses in developing transparent inorganic glass–ceramics phosphors excitable by blue chip, as an alternative to conventional polymer-based phosphor converter, for construction of high-power white light-emitting diodes. Two kinds of synthesis routes, glass crystallization and low-temperature co-sintering, are discussed in detail. Afterwards, the materials design, structure/property optimization as well as glass–ceramic-based WLED devices construction are summarized. Finally, challenges and future advances for the realization of transparent glass–ceramics in commercial applications will be presented.

445 citations

Journal ArticleDOI
TL;DR: In this article, the authors present the most recent breakthroughs in these attempts from many different research groups published during the last five years, focusing in polymeric systems and their composites.
Abstract: Self-healing materials are attracting increasing interest of the research community, over the last decades, due to their efficiency in detecting and “autonomically” healing damage. Numerous attempts are being presented every year focusing on the development of different self-healing systems as well as their integration to large scale production with the best possible property–cost relationship. The current work aims to present the most recent breakthroughs in these attempts from many different research groups published during the last five years. The current review focuses in polymeric systems and their composites. The reviewed literature is presented in three distinct categories, based on three different scopes of interest. These categories are (i) the materials and systems employed, (ii) the experimental techniques for the evaluation of materials properties and self-healing efficiency of the materials/structures and (iii) the characterization techniques utilized in order to evaluate (off-line) and monitor (on-line) the healing efficiency of the proposed systems. Published works are presented separately in all the different categories, thus the interested reader is advised to follow the structure of the review and refer to the chapter of interest.

418 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a review of the state-of-the-art LED packaging and application technologies, focusing on heat generation in chips, heat flow in packages and application products, fluid flow in phosphor coating process, etc.

350 citations