• Journal of Communications and Networks
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• 제13권6호
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• pp.655-663
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• 2011

Diffuse optical wireless (DOW) systems have the advantage that they do not require point-to-point siting so one transmitter can communicate with several receivers. In this paper, we investigate multiple access scheduling methods for downlink orthogonal frequency division multiplexing (OFDM) in diffuse optical wireless networks. Unlike the radio frequency (RF) channel, the DOW channel has low-pass filter characteristics and so requires different scheduling methods than those developed for the RF channel. Multi-user diversity orthogonal frequency division multiple access (OFDMA) systems nominate a cluster of subcarriers with the largest signal-to-noise-ratio for transmission. However, in a DOW channel, most users would choose the lowest frequency clusters of subcarriers. To remedy this problem, we make two proposals. The first is to use a variable cluster size across the subcarriers; the lower frequency clusters will have fewer subcarriers while the higher frequency clusters will have more subcarriers. This will equalize the capacity of the clusters. The second proposal is to randomize a user's cluster selection from a group of clusters satisfying a minimum threshold. Through simulation it is shown that combining these strategies can increase the throughput while ensuring a fair distribution of the available spectrum.

• 미생물과산업
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• 제15권1호
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• pp.38-42
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• 1989

Industrial strain Improvement is concerned with developing or modifying microorga-nisms used In production of commercially important fermentation products. The aim is to reduce the production cost by improving productivity of a strain and manipulating specific cilarafteristic such as the ability to utilize cheaper raw materials or resist bacteriophages. The traditional empiri-cal approach to strain improvement is mutation combined with selection and breeding techniques. It is still used by us to improve the productivity of organisms in amino acids. organic acids andenzymes production. The breeding of high L-lysine-producing strain Au112 is one of the outstanding examples of this approach. It is it homoserine auxotroph with AEC, TA double metabolicanalogue resistant markers. The yield reaches 100g/1. Resides, the citric acid-producing organism Aspergillus nuger, Co827, its productivity reches the advanced level in the world, is also the result of a series mutations expecially with Co Y-radiation. The thermostable a-amylaseroducing strain A 4041 is the third example. By combining physical and chemical multations. the strain ,A 4041becomes an asporogenous, catabolite derepressed mutant with rifamycin resistant and methionine, arginine auxotroph markers. The a-amylase activity reaches 200 units/ml. The fourth successful example of mutation in strain improvement is the glucoamylase-producing strain Aspergillus nigerSP56 its enzyme activity is 20,000 units/ml, 4 times of that of the parental strain UV_11. Recently recombinant DNA approach Provides a worth while alternative strategy to Industrial strain improve-ment. This technique had been used by us to increase the thermostable a-amylase production and on some genetic researches.

• 한국통신학회논문지
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• 제35권1B호
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• pp.136-143
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• 2010

본 논문에서는 임의로 분포되어 있는 레일리 페이딩(Rayleigh fading) 채널 하에서 소스노드와 목적지 노드 사이의 직접 경로가 존재하고 복호 후 전송(decode-and-forward) 방식을 사용하여 중계하는 시스템을 고려한다. 이때, 다수의 릴레이 가운데 베스트 릴레이를 선택하여 이중 홉을 사용하여 통신하는 경우와 다중 홉을 사용하여 통신하는 경우의 아웃티지 확률을 구하고, 이를 통해 그 성능을 비교한다. 여기서 소스 노드와 릴레이들로부터 목적지 노드가 받은 모든 신호는 maximum ratio combining (MRC) 기법을 사용하여 결합하였고, 모든 경우에 대하여 목적지 노드에서 받은 수신 신호의 SNR이 갖는 확률 밀도 함수(probability density function, PDF)와 누적 확률 변수(cumulative density function, CDF)를 유도하였다. 이와 같이 구한 아웃티지 확률을 통해 릴레이의 개수가 2개일 때를 가정하고 실험한 결과, 채널 상태가 나쁠수록 다중 홉을 사용하여 통신하는 기법이 베스트 릴레이 선택 기법보다 좋은 성능을 보였다.

• Journal of Communications and Networks
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• 제14권1호
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• pp.91-103
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• 2012

Network mobility (NEMO) based on mobile IP version 6 has been proposed for networks that move as a whole. Route optimization is one of the most important topics in the field of NEMO. The current NEMO basic support protocol defines only the basic working mode for NEMO, and the route optimization problem is not mentioned. Some optimization schemes have been proposed in recent years, but they have limitations. A new NEMO route optimization scheme-involving a combination of the optimized route cache protocol (ORC) and reverse routing header (RRH) and the use of a quota mechanism for optimized sessions (OwR)-is proposed. This scheme focuses on balanced performance in different aspects. It combines the ORC and RRH schemes, and some improvements are made in the session selection mechanism to avoid blindness during route optimization. Simulation results for OwR show great similarity with those for ORC and RRH. Generally speaking, the OwR's performance is at least as good as that of the RRH, and besides, the OwR scheme is capable of setting up optimal routing for a certain number of sessions, so the performance can be improved and the cost of optimal routing in nested NEMO can be decreased.

• Industrial Engineering and Management Systems
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• 제15권1호
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• pp.11-18
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• 2016

This paper considers a scheduling problem in a flexible job shop with a reconfigurable manufacturing cell. The flexible job shop has both operation and routing flexibilities, which can be represented in the form of a multiple process plan, i.e. each part can be processed through alternative operations, each of which can be processed on alternative machines. The scheduling problem has three decision variables: (a) selecting operation/machine pairs for each part; (b) sequencing of parts to be fed into the reconfigurable manufacturing cell; and (c) sequencing of the parts assigned to each machine. Due to the reconfigurable manufacturing cell's ability of adjusting the capacity, functionality and flexibility to the desired levels, the priority scheduling approach is proposed in which the three decisions are made at the same time by combining operation/machine selection rules, input sequencing rules and part sequencing rules. To show the performances of various rule combinations, simulation experiments were done on various instances generated randomly using the experiences of the manufacturing experts, and the results are reported for the objectives of minimizing makespan, mean flow time and mean tardiness, respectively.

• Journal of Information Processing Systems
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• 제10권4호
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• pp.602-617
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• 2014

The performance of a cognitive radio network (CRN) solely depends on how precisely the secondary users can sense the presence or absence of primary users. The incorporation of a spatial false alarm makes deriving the probability of a correct decision a cumbersome task. Previous literature performed this task for the case of a received signal under a Normal probability density function case. In this paper we enhance the previous work, including the impact of carrier frequency, the gain of antennas on both sides, and antenna heights so as to observe the robustness against noise and interference and to make the correct decision of detection. Three small scale fading channels: Rayleigh, Normal, and Weibull were considered to get the real scenario of a CRN in an urban area. The incorporation of a maximal-ratio combining and selection combing with a variation of the number of received antennas have also been studied in order to achieve the correct decision of spectral sensing, so as to serve the cognitive users. Finally, we applied the above concept to a traffic model of the CRN, which we based on a two-dimensional state transition chain.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권9호
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• pp.1573-1595
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• 2011

In this paper, the outage performance of multiuser multiple-input single-output (MISO) systems exploiting joint spatial and multiuser diversities is investigated for Rayleigh fading channels with outdated feedback. First, we derive closed-form exact outage probabilities for the joint diversity schemes that combine user scheduling with different spatial diversity techniques, including: 1) transmit maximum-ratio combining (TMRC); 2) transmit antenna selection (TAS); and 3) orthogonal space-time block coding (OSTBC). Then the asymptotic outage probabilities are analyzed to gain more insights into the effect of feedback delay. It is observed that with outdated feedback, the asymptotic diversity order of the multiuser OSTBC (M-OSTBC) scheme is equal to the number of transmit antennas at the base station, while that of the multiuser TMRC (M-TMRC) and the multiuser TAS (M-TAS) schemes reduce to one. Further by comparing the asymptotic outage probabilities, it is found that the M-TMRC scheme outperforms the M-TAS scheme, and the M-OSTBC scheme can perform best in the outage regime of practical interest when the feedback delay is large. Theoretical analysis is verified by simulation results.

• 한국멀티미디어학회논문지
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• 제11권12호
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• pp.1635-1648
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• 2008

The extraction of important features in cancer cell image analysis is a key process in grading renal cell carcinoma. In this study, we applied three-dimensional (3D) texture feature extraction methods to cell nuclei images and evaluated the validity of them for computerized cell nuclei grading. Individual images of 2,423 cell nuclei were extracted from 80 renal cell carcinomas (RCCs) using confocal laser scanning microscopy (CLSM). First, we applied the 3D texture mapping method to render the volume of entire tissue sections. Then, we determined the chromatin texture quantitatively by calculating 3D gray-level co-occurrence matrices (3D GLCM) and 3D run length matrices (3D GLRLM). Finally, to demonstrate the suitability of 3D texture features for grading, we performed a discriminant analysis. In addition, we conducted a principal component analysis to obtain optimized texture features. Automatic grading of cell nuclei using 3D texture features had an accuracy of 78.30%. Combining 3D textural and 3D morphological features improved the accuracy to 82.19%. As a comparative study, we also performed a stepwise feature selection. Using the 4 optimized features, we could obtain more improved accuracy of 84.32%. Three dimensional texture features have potential for use as fundamental elements in developing a new nuclear grading system with accurate diagnosis and predicting prognosis.

• 대한두경부종양학회지
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• 제35권1호
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• pp.1-11
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• 2019

In head and neck reconstruction, microsurgeons are faced with various demands, such as thin resurfacing, or three-dimensional reconstruction, and therefore, conventional flap as well as perforator flaps are all useful for the functional and aesthetic reconstruction successfully. Among perforator flaps, the pros and cons of anterolateral thigh perforator flap(ALTp) and thoracodorsal perforator flap(TAp) is compared and selected depending on the surgeon's preference, recipient site condition or patient status. Both flaps can be elevated in a chimeric pattern by combining different aspects of tissue components. Customized or tailored reconstruction as well as 3 dimensional reconstructions are all available with perforator flaps and it is useful in head and neck reconstruction. The most outstanding update in head and neck reconstruction is the perforator based island flap (PBIF) compared to conventional flaps. The conventional local flap has evolved on behalf of the perforator concept and its design becomes more flexible and freestyle with less limitations. Actually, random pattern flap is now a misnomer and most conventional local flaps turn into PBIFs. Finally we can say all conventional donor site becomes universal, depending on the surgeons' preference or idea. Moreover, there is no more "flap of choice" and postoperative results are quite variable by surgeons' ability. Operative procedures and plans are very flexible to freestyle flap. With all these advantages, surgeons should be armed with both conventional and perforator concepts for solving any defects or problems.

• 안보군사학연구
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• 통권15호
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• pp.117-151
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• 2018

The development of local defense parts has played a role a pure function such as maintenance of stable procurement source of military goods, provision of timely supply, establishment of self-defense base, creation of import substitution effect considering the whole life-cycle cost, reduction of foreign currency and protection of domestic defense industry. However, as the development success rate is deteriorating, it is time to analyze the related policies and improve the system. In order to improve the success rate of development of parts for the defense sector, it is necessary to unify the separated policies by the development-related departments and strengthen the policy support for the development companies to actively participate in the development. In addition, it is necessary to improve the paradigm for the selection of development items and change the authority of selecting development items and to delegate authority to create synergies. Parts localization development policy improvement is military support side it will contribute to strengthening defense power management by organically combining with technological development aspect and economical aspect. Development items will be linked to defense exports, which will have a remarkable effect on sales growth and job creation effects. The development of local defense parts is spreading.