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981.
Minimizing the number of tardy jobs in a single-machine scheduling problem with periodic maintenance
Ju-Yong LeeYeong-Dae Kim 《Computers & Operations Research》2012,39(9):2196-2205
This research focuses on the problem of scheduling jobs on a single machine that requires periodic maintenance with the objective of minimizing the number of tardy jobs. We present a two-phase heuristic algorithm in which an initial solution is obtained first with a method modified from Moore's algorithm for the problem without maintenance and then the solution is improved in the second phase. Performance of the proposed heuristic algorithm is evaluated through computational experiments on randomly generated problem instances and results show that the heuristic gives solutions close to those obtained from a commercial integer programming solver in much shorter time and works better than an existing heuristic algorithm in terms of the solution quality. 相似文献
982.
Henrik Aanæs Anders Lindbjerg Dahl Kim Steenstrup Pedersen 《International Journal of Computer Vision》2012,97(1):18-35
Not all interest points are equally interesting. The most valuable interest points lead to optimal performance of the computer
vision method in which they are employed. But a measure of this kind will be dependent on the chosen vision application. We
propose a more general performance measure based on spatial invariance of interest points under changing acquisition parameters
by measuring the spatial recall rate. The scope of this paper is to investigate the performance of a number of existing well-established
interest point detection methods. Automatic performance evaluation of interest points is hard because the true correspondence
is generally unknown. We overcome this by providing an extensive data set with known spatial correspondence. The data is acquired
with a camera mounted on a 6-axis industrial robot providing very accurate camera positioning. Furthermore the scene is scanned
with a structured light scanner resulting in precise 3D surface information. In total 60 scenes are depicted ranging from
model houses, building material, fruit and vegetables, fabric, printed media and more. Each scene is depicted from 119 camera
positions and 19 individual LED illuminations are used for each position. The LED illumination provides the option for artificially
relighting the scene from a range of light directions. This data set has given us the ability to systematically evaluate the
performance of a number of interest point detectors. The highlights of the conclusions are that the fixed scale Harris corner
detector performs overall best followed by the Hessian based detectors and the difference of Gaussian (DoG). The methods based
on scale space features have an overall better performance than other methods especially when varying the distance to the
scene, where especially FAST corner detector, Edge Based Regions (EBR) and Intensity Based Regions (IBR) have a poor performance.
The performance of Maximally Stable Extremal Regions (MSER) is moderate. We observe a relatively large decline in performance
with both changes in viewpoint and light direction. Some of our observations support previous findings while others contradict
these findings. 相似文献
983.
Sangjin Sung Gunhee Jang Kyungjin Kang Jiyeon Kim Dohyun Park Donghun Choi 《Microsystem Technologies》2012,18(9-10):1359-1364
A conventional hard disk drive (HDD) spindle motor has a pulling plate to generate the axial magnetic force. However, the pulling plate consumes significant amount of iron loss due to the alternating magnetic field on the pulling plate. We propose the new design of a HDD spindle motor with pulling magnet to generate the pre-load as well as to eliminate the iron loss of the pulling plate. We also develop an optimal design methodology to minimize iron and copper losses from the spindle motor of a computer HDD while maintaining the same level of torque ripple and pulling force. The new design is optimized by the developed optimal design methodology. A metamodel is constructed from the three-dimensional finite element analysis of the magnetic field and the meta-modeling techniques, and the accuracies of the metamodels are discussed. The proposed optimal design problem is solved by the progressive quadratic approximation method. The proposed design reduces the electrical loss of the HDD spindle motor by 30.42?% while maintaining the same level of torque ripple and pulling force. 相似文献
984.
985.
Sung-Yong Lim Nakyeong Kim Kyuil Jung Jae-Seong Lee Yoon-Koo Kang Hyunseok Yang Kyoung-Su Park No-Cheol Park Young-Pil Park 《Microsystem Technologies》2012,18(9-10):1711-1717
Page-oriented holographic data storage (HDS) is very sensitive to disturbances that affect the position of the recording medium. Accordingly, a more precise tracking servo is required for the recording process, and is also crucial for achieving high storage density. A compensation method is therefore essential for HDS recording. In this paper, we suggest some discrete pre-patterns for the tracking servo used in the recording process. This method is motivated by a tracking servo technique for a hard disk drive. Firstly, in designing the pattern shape, HDS characteristics are taken into account. Secondly, track error signals are analyzed. Thirdly, the discrete pre-pattern intervals are determined according to the track tolerance. Lastly, the feasibility of the new method is analyzed via simulations and experiments. 相似文献
986.
A new dimmer using a mental-oxide-semiconductor field-effect transistor (MOSFET) for alternating-current (AC) directly driven
light-emitting-diode (LED) lamp was presented. The control method of proposed dimmer is pulse width control (PWM) method.
Compared with the conventional phase-controlled dimmer, the proposed PWM dimmer can produce sine wave and did not cause harmonics
problem. Furthermore, the proposed control method did not amplify the light flicker due to the independence of input voltage.
Therefore, the PWM dimmer can be used as the dimmer of the AC LED lamp instead of the conventional phase-controlled dimmer.
The experimental result shows that the proposed PWM dimmer has good performances. 相似文献
987.
王洪梅 KIM Jae-hyung LEE Sang-hyuk KIM Hyung-jung KIM Jin-up KOH Jong-seog 《中南工业大学学报(英文版)》2012,19(2):408-416
The problem of designing a digital frontend (DFE) was considered which can dynamically access or sense dual bands in any radio
frequency (RF) regions without requiring hardware changes. In particular, second-order bandpass sampling (BPS) as a technique
that enables to realize the multiband reception function was discussed. In a second-order BPS system, digital reconstruction
filters were utilized to eliminate the interferences generated while down converting arbitrarily positioned RF-band signals
by using the direct digitization method. However, the inaccuracy in the phase shift or the amplitude mismatch between the
two sample streams may cause insufficient rejection of interference. Practical problems were studied, such as performance
degradation in signal-to-interference ratio (SIR) and compensation methods to overcome them. In order to demonstrate the second-order
BPS as a flexible DFE suitable for software-defined radio (SDR) or cognitive radio (CR), a DFE testbed with a reconfigurable
structure was implemented. Moreover, with a view to further demonstrate the proposed compensation algorithms, experimental
results show that dual bands are received simultaneously. 相似文献
988.
The direct current-direct current (DC-DC) converter is designed for 1 T static random access memory (SRAM) used in display
driver integrated circuits (ICs), which consists of positive word-line voltage (V
PWL), negative word-line voltage (V
NWL) and half-V
DD voltage (V
HDD) generator. To generate a process voltage temperature (PVT)-insensitive V
PWL and V
NWL, a set of circuits were proposed to generate reference voltages using bandgap reference current generators for respective
voltage level detectors. Also, a V
PWL regulator and a V
NWL charge pump were proposed for a small-area and low-power design. The proposed V
PWL regulator can provide a large driving current with a small area since it regulates an input voltage (VCI) from 2.5 to 3.3
V. The V
NWL charge pump can be implemented as a high-efficiency circuit with a small area and low power since it can transfer pumped
charges to V
NWL node entirely. The DC-DC converter for 1 T SRAM were designed with 0.11 μm mixed signal process and operated well with satisfactory
measurement results. 相似文献
989.
Work performed on scaffolds carries the risk of falling that disproportionately threatens the safety and health of novice construction workers. Hence, objective measures of the postural stability, cardiovascular stress, and subjective difficulty in maintaining postural balance were evaluated for four expert and four novice construction workers performing a manual task in a standing posture on a scaffold with and without safety handrails at two different elevation heights. Based on a multivariate analysis of variance, the experience, scaffold height, and presence of a handrail were found to significantly affect measures of the postural stability and cardiovascular stress. At a lower level of worker experience, a higher scaffold height, and in the absence of a handrail (which may correspond to higher risk of a fall), postural stability was significantly reduced, while cardiovascular stress and subjective difficulties in maintaining postural balance increased. We emphasize the importance of training and handrails for fall prevention at construction sites. 相似文献
990.
PLM (Product Lifecycle Management) as well as enterprise information systems commonly use the BOM (Bill of Material) as a means of communication during product development. BOM has been used for product design, production scheduling, procurement, manufacturing and maintenance as it contains the part list of a subassembly or assembly product. BOM currently plays a key role in the PLM environment because it is an essential product information platform in the industry. In practice, product data should be arranged based on the BOM and product structure. Many shipyards or PLM vendors have attempted to develop a PLM adequate for shipbuilding. However, it is always the premise of the successful PLM implementation to prepare the efficient product structure and BOM.This paper suggests an enterprise BOM which addresses the hierarchy of parts and assembly, product structure and product information of outfitting equipment in marine vessel design. In order to express the evolution of product structures and outfitting information during the ship design, the enterprise BOM is modeled by the structure BOM and the display BOM. Concepts are developed for modeling all levels of product relations with a uniform set of relationships supported by the enterprise BOM. It is shown that the architecture of the structure BOM can be used to define the relationships between assemblies, parts, and a multi-view of an evolutional BOM in ship design. The architecture of the outfitting BOM is also presented using an example of a piping system. 相似文献