Numerical simulation and experimental validation of heat sinks fabricated using selective laser melting for use in a compact LED recessed downlight

The aim of this study was to design and fabricate heat sinks with high heat dissipation capacity by using selective laser melting (SLM). A low junction temperature was maintained and the lifetime and reliability of the resultant compact LED recessed downlight (CLDL) was increased. A trapezoidal-finned heat sink with horizontal holes (HFSLM) and three-dimensional metal-foam-like heat sink (3DSLM), which both have large surface-area-to-volume ratios, were designed in this study. Each heat sink was mounted to a 10 W CLDL and installed in a test box with the dimensions 105 mm × 105 mm × 100 mm (L × W × H) for evaluating the lifespan of the CLDL in a high-temperature environment with natural convection. The downlights withstood the test, and according to the Arrhenius equation, they had a long lifetime at normal usage temperatures. The results of the stationary simulations agreed with the experimental results. The temperatures at the solder point of the CLDL with the HFSLM and 3DSLM were 88.6 and 91.4 °C, respectively, corresponding to LED junction temperatures of 118.6 and 121.4 °C. These junction temperatures were lower than the specified LED limit temperature of 135 °C. The results of an accelerated life test prediction and in situ temperature measurement testing based on TM-21 extrapolations using LM-80 data indicated that the lumen maintenance of the CLDLs complied with Energy Star^® requirements.

     

薄壁件选择性激光熔融的分区扫描路径规划

残余应力容易导致采用选择性激光熔融技术加工的薄壁件变形甚至开裂,为了减少残余应力并控制其分布,提出了一种基于中轴变换的分区扫描路径规划策略.首先对分层实体区域进行中轴变换,然后根据裁剪后的中轴将分层实体区域划分为主区域和连接区域,针对主区域和连接区域分别设计了正弦曲线形扫描路径和正三角网格式扫描路径,最后给出了一个典型...     

Optimal displacement amplification ratio of bridge-type compliant mechanism flexure hinge using the Taguchi method with grey relational analysis

Microsystem Technologies - The compliant mechanism flexure hinge has been frequently utilized in precision enginering in recent years, such as the bridge-type and rhombus-type compliant mechanisms....     

Machine learning-based optimization of process parameters in selective laser melting for biomedical applications

Journal of Intelligent Manufacturing - Titanium-based alloy products manufactured by Selective Laser Melting (SLM) have been widely used in biomedical applications, owing to their high...     

Design,analysis and validation of the bridge-type displacement amplification mechanism with circular-axis leaf-type flexure hinges for micro-grasping system

Microsystem Technologies - For stable and flexible manipulation, realizing parallel grasping and large output stroke simultaneously has become a key issue in the researches on micro-grasping...     

An automatic measurement system for the wall thickness of corrugated plate based on laser triangulation method

Wall thickness is an important parameter used in the characterization of the surface quality of chevron corrugated plates. However, current measurement techniques such as contact mechanical or destructive modes are timing-consuming and are limited by the complex morphology of the measured object. In this study, an optical measurement system is established for experimental evaluation of the wall thickness. Its optical design and working characteristic are described based on the triangulation principle. By performing normal vector estimation, and combining with the search results about the best possible reconstructed mesh surface, the wall thickness at each measurement point can be evaluated. A series of comparison experiments with the maximum deviation 0.043 mm show that our proposed method can provide effective and automatic technical support for dimensional detection of complex components.     

Development of a novel system for in-situ repair of aeroengine airfoil via pulsed laser ablation

A novel system for performing in-situ micro-machining of aero-engines for repair applications is proposed in this paper. Using Pulsed Laser Ablation (PLA) as material removal technique, surface cracks caused by foreign objects colliding with airfoils are removed by performing a layer-by-layer micro-machining in the area surrounding the damaged zone. Compared to conventional repair performed by micro-grinding, our invasive PLA system demonstrates a similar level of performance, evaluated from the point of view of fatigue strength in the high cycle (>10⁷) regime. The follow-up fractographic and metallurgical analysis, indicated that although some microstructural characteristics are different between the repair methods, the incurred surface damage is limited in magnitude to a thin surface layer (<30 μm) and the influence on fatigue life is comparable. In the last section, a novel prototype system is presented which allows performing the PLA repair in-situ by use of a miniaturized laser scanning head coupled with a flexible mechanical deployment arm. The system has been successfully tested inside a Roll-Royce Trent jet engine; effectively this proves the possibility of performing in-situ laser micro-machining inside complex mechanical systems such as aero-engines, without the need for complex/expensive disassembly.     

Scheduling in a two-machine flowshop for the minimization of the mean absolute deviation from a common due date

This paper addresses the minimization of the mean absolute deviation from a common due date in a two-machine flowshop scheduling problem. We present heuristics that use an algorithm, based on proposed properties, which obtains an optimal schedule for a given job sequence. A new set of benchmark problems is presented with the purpose of evaluating the heuristics. Computational experiments show that the developed heuristics outperform results found in the literature for problems up to 500 jobs.     

Study on mobile mechanism of a climbing robot for stair cleaning: a translational locomotion mechanism and turning motion

In human living environments, it is often the case that the cleaning area is three-dimensional space such as a high-rise building. An autonomous cleaning robot is proposed so as to move on all floors including stairs in a building. When a robot cleans in three-dimensional space, it needs to turn for direction in addition to climb down stairs. The proposed robot selects movement using legs or wheels depending on stairs or flat surfaces. In this paper, a mobile mechanism and a control method are described for translational locomotion. The translational mechanism is based on using two-wheel-drive type omni-directional mobile mechanism. To recognize a stair using the position-sensitive detector, the robot shifts from translational locomotion to climbing down motion or edge-following motion. It is shown that the proposed robot turns to face a stair with the accuracy of 5°.     

Study on the effect of heating plate thickness on the micro induction heater for thermal bubbles generation

This paper designed a micro planar induction heater for thermal bubbles generation. The micro heater which consists of a micro planar coil, a copper heating plate and a glass slide was fabricated with MEMS fabrication process. The relations between the heating performance and the thickness of heating plate were studied in the simulation with the software of COMSOL. The experimental system has been built and the experimental tests for thermal bubble generation have been also carried out with the prototype. The process of thermal bubbles generation was recorded by the video camera. The frequency of AC current applied in the experiment is 100 kHz and the heating time of 1 s. The experimental results indicated that the micro heater has the best heating performance with the heating plate thickness of 12–16 μm, and the minimum power for thermal bubbles generation was only 0.427 W. This micro heater can be applied to a variety of thermal bubble devices, such as micro actuator, micro ejector and micro pump.     

Understanding the molecular mechanism and regioselectivity in the synthesis of celecoxib via a domino reaction: A DFT study

The molecular mechanism and energetic of the domino reaction involved in the synthesis of celecoxib, a well-known anti-inflammatory drug, were theoretically studied at the DFT-B3LYP/6-31G^* level. The first reaction in this domino process, which is also the rate-determining step, is a complete regioselective [3 + 2] cycloaddition (32CA) reaction associated with the nucleophilic attack of C5 carbon atom of enamine 7 on the C3 carbon atom of nitrile imine 6, leading to cycloadduct 8. The second reaction is a rapid acid/base catalysed stepwise elimination reaction of the morpholine 9 from cycloadduct 8 affording celecoxibe 3. The results also show that neither molecular mechanism of reaction nor activation barriers are considerably affected by the inclusion of solvent. The calculated relative Gibbs free energies as well as local reactivity indices obtained using the calculated Parr functions explain the complete regioselective fashion provided by the 32CA reaction under consideration in excellent agreement with the experimental findings.     

The possibilities of a strontium vapor laser using for laser sensing of minor gaseous components of the atmosphere

The present work studies the possibility of application of the multiwavelength laser on SrI and SrII self-terminated transitions for laser remote sensing of minor gaseous components (MGC) and meteorological parameters of the atmosphere using the differential absorption lidar (DIAL) method. The article is published in the original.     

A method for the calibration of a 3-D laser scanner

The calibration of a three-dimensional digitizer is a very important issue to take into consideration that good quality, reliability, accuracy and high repeatability are the features which a good digitizer is expected to have. The aim of this paper is to propose a new method for the calibration of a 3-D laser scanner, mainly for robotic applications. The acquisition system consists of a laser emitter and a webcam with fixed relative positions. In addition, a cylindrical lens is provided with the laser housing so that it is capable to project a plane light. An optical filter was also used in order to segment the laser stripe from the rest of the scene. For the calibration procedure it was used a digital micrometer that move a target with known dimensions. The calibration method is based on the modeling of the geometrical relationship between the 3-D coordinates of the laser stripe on the target and its digital coordinates in the image plane. By this method it is possible to calibrate the intrinsic parameters of the video system, the position of the image plane and the laser plane in a given frame, all in the same time.     

Improving cache locking performance of modern embedded systems via the addition of a miss table at the L2 cache level

To confer the robustness and high quality of service, modern computing architectures running real-time applications should provide high system performance and high timing predictability. Cache memory is used to improve performance by bridging the speed gap between the main memory and CPU. However, the cache introduces timing unpredictability creating serious challenges for real-time applications. Herein, we introduce a miss table (MT) based cache locking scheme at level-2 (L2) cache to further improve the timing predictability and system performance/power ratio. The MT holds information of block addresses related to the application being processed which cause most cache misses if not locked. Information in MT is used for efficient selection of the blocks to be locked and victim blocks to be replaced. This MT based approach improves timing predictability by locking important blocks with the highest number of misses inside the cache for the entire execution time. In addition, this technique decreases the average delay per task and total power consumption by reducing cache misses and avoiding unnecessary data transfers. This MT based solution is effective for both uniprocessors and multicores. We evaluate the proposed MT-based cache locking scheme by simulating an 8-core processor with 2 levels of caches using MPEG4 decoding, H.264/AVC decoding, FFT, and MI workloads. Experimental results show that in addition to improving the predictability, a reduction of 21% in mean delay per task and a reduction of 18% in total power consumption are achieved for MPEG4 (and H.264/AVC) by using MT and locking 25% of the L2. The MT results in about 5% delay and power reductions on these video applications, possibly more on applications with worse cache behavior. For the FFT and MI (and other) applications whose code fits inside the level-1 instruction (I1) cache, the mean delay per task increases only by 3% and total power consumption increases by 2% due to the addition of the MT.     

非接触电能传输系统电容补偿机理研究

基于磁耦合谐振非接触电能传输系统中几种不同的电容补偿方式,分析了接收端采用不同补偿方式时反射阻抗与频率的关系,探讨了发射端补偿电容的优化条件,推导了不同补偿方式下系统传输功率的表达式,进一步分析了补偿方式对传输功率的影响。理论分析与仿真结果表明,发射端采用串联补偿、接收端采用并联补偿时,非接触电能传输系统性能最佳。     

Modeling of the relative humidity via functional networks and control of the temperature via classic controls for a bird incubator

The control of the relative humidity and the temperature is important for the birds to be born. It is not easy to control the relative humidity, but it is possible to obtain the measure of the relative humidity as a consequence of the control of the temperature in a bird incubator. In this article, (1) the mathematical model for the control of temperature in the bird incubator is presented, (2) a functional network to approximate the relative humidity behavior in the bird incubator is proposed, (3) a control for the temperature in the bird incubator is proposed, the error of the proportional control applied to the mathematical model of the temperature of the bird incubator is assured to be uniformly stable, (4) the comparison results of four classic control laws for the control of the temperature considering the proposed mathematical model of the temperature and the functional network to approximate the relative humidity behavior in the bird incubator are presented.     

Control for the synchronization of Chen system via a single nonlinear input

This paper addresses control for the synchronization of Chen chaotic systems via sector nonlinear inputs. Feedback control, adaptive control, fast sliding mode and robust control approaches based on single state feedback controller are investigated. In these cases, sufficient conditions for the synchronization are obtained analytically. Numerical simulations verify the control performances.     

Control for the synchronization of Chen system via a single nonlinear input

This paper addresses control for the synchronization of Chen chaotic systems via sector nonlinear inputs. Feedback control, adaptive control, fast sliding mode and robust control approaches based on single state feedback controller are investigated. In these cases, sufficient conditions for the synchronization are obtained analytically. Numerical simulations verify the control performances.