• Title/Summary/Keyword: Ramp-up Problem

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Hybrid Artificial Immune System Approach for Profit Based Unit Commitment Problem

  • Lakshmi, K.;Vasantharathna, S.
    • Journal of Electrical Engineering and Technology
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    • v.8 no.5
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    • pp.959-968
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    • 2013
  • This paper presents a new approach with artificial immune system algorithm to solve the profit based unit commitment problem. The objective of this work is to find the optimal generation scheduling and to maximize the profit of generation companies (Gencos) when subjected to various constraints such as power balance, spinning reserve, minimum up/down time and ramp rate limits. The proposed hybrid method is developed through adaptive search which is inspired from artificial immune system and genetic algorithm to carry out profit maximization of generation companies. The effectiveness of the proposed approach has been tested for different Gencos consists of 3, 10 and 36 generating units and the results are compared with the existing methods.

A Study on the Image Sticking Phenomenon in AC PDP (AC PDP의 Image Sticking 현상에 관한 연구)

  • Lim, Sung-Hyun;Shim, Kyoung-Ryul;Kim, Dong-Hyun;Lee, Ho-Joon;Park, Chung-Hoo;Kim, Gyu-Seob
    • Proceedings of the KIEE Conference
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    • 2002.07c
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    • pp.1640-1643
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    • 2002
  • Image sticking, the phenomenon that the previously displayed pattern still remains after the image is changed into different image, is one of the most serious problem in realizing high picture quality. In this paper, we tried characterizing this undesirable feature in terms of the luminance and the intial firing voltage at ramp up time in reset period. It was found that the cell located at the boundary of previous image pattern show low firing voltage and high background luminance. And the results show that the degree of the image sticking is severely affected by discharge duration and the length of the sustain period.

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Characteristics of Image Sticking Observed During Background Display in AC-PDP (AC PDP의 배경광 잔상특성)

  • 류재화;임성현;김동현;김중균;이호준;박정후
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.53 no.2
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    • pp.91-96
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    • 2004
  • In darkroom condition, it was observed that a white picture pattern lasted several minutes leaves a recognizable trace in subsequent black background picture. Although this is not a serious problem for the most current public display or home TV applications, the image sticking should be minimized for future high quality multimedia display applications. In order to characterize this picture memory effect having relatively long time scale, spatially resolved luminance measurement and light waveform measurement have been performed. Pixels located at the outer boundary of white pattern previously displayed shows highest luminance. These cells also shows fastest ignition at the ramp up reset sequence. The luminance and ignition voltage differences between boundary cells and the other cells are increased with display duration and number of sustain-pulse. It is speculated that image sticking observed at the boundary cell is originated from the transport of charged particles and re-deposition of reactive species such as Mg, O provided from strong sustain discharge region.

The study on the image sticking phenomenon in AC PDP (AC PDP의 Image sticking 현상에 대한 연구)

  • Lim, Sung-Hyun;Shim, Kyoung-Ryul;Kim, Dong-Hyun;Lee, Ho-Joon;Park, Chung-Hoo;Kim, Gyu-Seob
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.05a
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    • pp.158-161
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    • 2002
  • Among the characteristics of image quality in AC PDP, the serious problem is the image sticking. It can be explained that the previous pattern still remains after the image is changed into different image. In this paper, in case that the length of sustain period and the continued time of still image is varied, the image sticking phenomenon is investigated as the Initial firing voltage at ramp up time during reset period.

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Design and Experiment investigation of disk bump to improve unload performance in HDD (HDD에서 언로드 성능향상을 위한 디스크 범프의 설계 및 실험 연구)

  • Lee, Hyung-Jun;Lee, Yong-Hyun;Park, Gyeong-Su;Park, No-Cheol;Park, Young-Pil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2007.05a
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    • pp.833-836
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    • 2007
  • Load/Unload technology has more benefits than the conventional CSS technology. However, it remains unsolved technical problem on the unloading process. While the slider climbs up the ramp at the outer edge of the disk, the possibility of the slider-disk contact by lift-off force and rebound of the slider increases. This paper focuses on no slider-disk contact. To prevent the slider-disk contact, we apply the disk bump on disk outer edge proceeding unload. Firstly, in the simulation, the bump dimension is determined by changing bump design parameters. Secondly, dynamic stability of slider have to be checked on disk bump before unload analysis, and unload analysis is performed by applying stable bump shapes to unload simulation. Thirdly, we select optimal bump shape to improve unload performance by unload analysis. Finally, in the experiment, the disk bump is mechanically manufactured by pressing disk surface using diamond tip. That is variously processed by changing pressing pressure. After confirming bump shape by nano-scanner, proper bump shape is applied to real experimental unload process. Through this investigation, we propose the optimal bump design to prevent the slider-disk contact, and then we can realize improved unloading performance.

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A Hybrid Multimedia Contents Recommendation Procedure for a New Item Problem in M-commerce (하이브리드 기법을 이용한 신상품 추천문제 해결방안에 관한 연구 : 모바일 멀티미디어 컨텐츠를 중심으로)

  • Kim Jae-Kyeong;Cho Yoon-Ho;Kang Mi-Yeon;Kim Hyea-Kyeong
    • Journal of Intelligence and Information Systems
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    • v.12 no.2
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    • pp.1-15
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    • 2006
  • Currently the mobile web service is growing with a tremendous speed and mobile contents are spreading extensively. However, it is hard to search what the user wants because of some limitations of cellular phones. And the music is the most popular content, but many users experience frustrations to search their desired music. To solve these problems, this research proposes a hybrid recommendation system, MOBICORS-music (MOBIle COntents Recommender System for Music). Basically it follows the procedure of Collaborative Filtering (CF) system, but it uses Contents-Based (CB) data representation for neighborhood formation and recommendation of new music. Based on this data representation, MOBICORS-music solves the new item ramp-up problem and results better performance than existing CF systems. The procedure of MOBICORS-music is explained step by step with an illustrative example.

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Effects of Root Gap on Residual Stresses and Deformation in the Multi-Pass Weld of Thick Plates for Steel Bridge (교량용 후판 다층용접시 잔류응력과 변형에 미치는 루트간격의 영향)

  • 장경복;김하근;강성수
    • Journal of Welding and Joining
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    • v.17 no.1
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    • pp.88-96
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    • 1999
  • The effects of root gap on welding residual stress and deformation are dealt with the multi-pass weldment with three kinds(0, 6, 30mm) of root gap by F.E.M common code, and then compared with experiment data. In this analysis, an 100% ramp heat input model was used to avoid numerical convergence problem due to an instantaneous increase in temperature near the fusion zone, and the effect of a moving arc in a two dimensional plane was also included. During the analysis, a small time increment was applied in a period with instantaneous temperature fluctuation while a large time increment was used in the rest period. The residual stress is distributed as symmetric types and maximum value is also equivalent when the weldment with 0mm and 6mm root gap is welded. In the case of 30mm root gap welding, the distribution of the residual stress extends over a wide range as asymmetric types due to the built-up weld, and most of the residual stress is biased in the side of a built-up weld part. In case of 0mm gap welding and 6mm gap welding, a little angular distortion occurs, but the level of deformation is small. When the weldment with 30mm root gap is welded, the angular deformation of the asymmetric types, however, occurs larger than the other specimens. The experimental and the analytic results show good coincidence and indicate that the welding residual stress and deformation distribution of 30 mm root gap specimen may be asymmetric and the amplitude is larger than those of root gap specimen under standard.

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Case Study on Design, Manufacture and Application of Customized Assistive Device for the ADL of Person with Brain Lesions (뇌병변장애인의 일상생활을 위한 맞춤형 보조기구의 설계·제작·적용 사례 연구)

  • Lee, J.H.;Choi, M.N.;Yim, S.B.;Rhee, G.M.
    • Journal of rehabilitation welfare engineering & assistive technology
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    • v.4 no.1
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    • pp.81-86
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    • 2010
  • This paper is case study on design, manufacture and application of customized assistive device for the ADL of person with brain lesions. The study had carried out from October 2010 to November 2010 and 2 clients from Assistive device case management demonstration project which is performed by Daegu assistive and rehabilitation center had participated. Case A, a 47-year-old man with brain lesions, stays only on the floor and could not get close to the usual toilet by himself because of the poor low extremities muscle strength and function. The moveable-toilet and customized ramp had applied to Case A. He clambers up the ramp and reach to the toilet easily. Case B, a 8-year-old boy with brain lesions, had difficulties with self-feeding because of his clumsy hand. Several existing feeding aids were applied but not appropriated. A customized feeding aid was designed and manufactured out of regard of Case A's ROM and right hand size. And his occupational therapist works together continuously to make him feed himself in the near future. Already-made assistive devices were not appropriate to Case A and B and to solve this problem, customized assistive devices were applied. The importance and needs of design and manufacture of assistive device were recognized through these case study.

A New Item Recommendation Procedure Using Preference Boundary

  • Kim, Hyea-Kyeong;Jang, Moon-Kyoung;Kim, Jae-Kyeong;Cho, Yoon-Ho
    • Asia pacific journal of information systems
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    • v.20 no.1
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    • pp.81-99
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    • 2010
  • Lately, in consumers' markets the number of new items is rapidly increasing at an overwhelming rate while consumers have limited access to information about those new products in making a sensible, well-informed purchase. Therefore, item providers and customers need a system which recommends right items to right customers. Also, whenever new items are released, for instance, the recommender system specializing in new items can help item providers locate and identify potential customers. Currently, new items are being added to an existing system without being specially noted to consumers, making it difficult for consumers to identify and evaluate new products introduced in the markets. Most of previous approaches for recommender systems have to rely on the usage history of customers. For new items, this content-based (CB) approach is simply not available for the system to recommend those new items to potential consumers. Although collaborative filtering (CF) approach is not directly applicable to solve the new item problem, it would be a good idea to use the basic principle of CF which identifies similar customers, i,e. neighbors, and recommend items to those customers who have liked the similar items in the past. This research aims to suggest a hybrid recommendation procedure based on the preference boundary of target customer. We suggest the hybrid recommendation procedure using the preference boundary in the feature space for recommending new items only. The basic principle is that if a new item belongs within the preference boundary of a target customer, then it is evaluated to be preferred by the customer. Customers' preferences and characteristics of items including new items are represented in a feature space, and the scope or boundary of the target customer's preference is extended to those of neighbors'. The new item recommendation procedure consists of three steps. The first step is analyzing the profile of items, which are represented as k-dimensional feature values. The second step is to determine the representative point of the target customer's preference boundary, the centroid, based on a personal information set. To determine the centroid of preference boundary of a target customer, three algorithms are developed in this research: one is using the centroid of a target customer only (TC), the other is using centroid of a (dummy) big target customer that is composed of a target customer and his/her neighbors (BC), and another is using centroids of a target customer and his/her neighbors (NC). The third step is to determine the range of the preference boundary, the radius. The suggested algorithm Is using the average distance (AD) between the centroid and all purchased items. We test whether the CF-based approach to determine the centroid of the preference boundary improves the recommendation quality or not. For this purpose, we develop two hybrid algorithms, BC and NC, which use neighbors when deciding centroid of the preference boundary. To test the validity of hybrid algorithms, BC and NC, we developed CB-algorithm, TC, which uses target customers only. We measured effectiveness scores of suggested algorithms and compared them through a series of experiments with a set of real mobile image transaction data. We spilt the period between 1st June 2004 and 31st July and the period between 1st August and 31st August 2004 as a training set and a test set, respectively. The training set Is used to make the preference boundary, and the test set is used to evaluate the performance of the suggested hybrid recommendation procedure. The main aim of this research Is to compare the hybrid recommendation algorithm with the CB algorithm. To evaluate the performance of each algorithm, we compare the purchased new item list in test period with the recommended item list which is recommended by suggested algorithms. So we employ the evaluation metric to hit the ratio for evaluating our algorithms. The hit ratio is defined as the ratio of the hit set size to the recommended set size. The hit set size means the number of success of recommendations in our experiment, and the test set size means the number of purchased items during the test period. Experimental test result shows the hit ratio of BC and NC is bigger than that of TC. This means using neighbors Is more effective to recommend new items. That is hybrid algorithm using CF is more effective when recommending to consumers new items than the algorithm using only CB. The reason of the smaller hit ratio of BC than that of NC is that BC is defined as a dummy or virtual customer who purchased all items of target customers' and neighbors'. That is centroid of BC often shifts from that of TC, so it tends to reflect skewed characters of target customer. So the recommendation algorithm using NC shows the best hit ratio, because NC has sufficient information about target customers and their neighbors without damaging the information about the target customers.