• ETRI Journal
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• v.38 no.3
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• pp.529-539
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• 2016

Recently, a product-matrix (PM) framework was proposed to construct optimal regenerating codes for homogeneous distributed storage systems (DSSs). In this paper, we propose an extended PM (EPM) framework for coding of heterogeneous DSSs having different repair bandwidths but identical storage capacities. Based on the EPM framework, an explicit construction of minimum remote-repair bandwidth regenerating (MRBR) codes is presented for a specific heterogeneous DSS, where two geographically different datacenters with associated storage nodes are deployed. The data reconstruction and regeneration properties of the MRBR code are proved strictly. For the purpose of demonstration, an example implementation of MRBR code is provided. The presented MRBR code is the first optimal strict-regenerating code for heterogeneous DSSs. In addition, our proposed EPM framework can be applied to homogeneous systems also.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1684-1691
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• 2016

Erasure codes have recently been applied to distributed storage systems due to their high storage efficiency. Regenerating codes are a kind of erasure codes, which are optimal in terms of minimum repair bandwidth. An (n,k,d)-regenerating code consists of n storage nodes where a failed node can be recovered with the help of the exactly d numbers of surviving nodes. However, if node failures occur frequently or network connection is unstable, the number of helper nodes that a failed node can contact may be smaller than d. In such cases, regenerating codes cannot repair the failed nodes efficiently since the node repair process of the codes does not work when the number of helper nodes is less than d. In this paper, we propose an operating method of regenerating codes where a failed node can be repaired from ${\bar{d}}$ helper nodes where $$k{\leq_-}{\bar{d}}{\leq_-}d$$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.11
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• pp.723-729
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• 2014

In this paper, we derive the average repair bandwidth and/or read cost for arbitrary repairable linear code ensembles. The repair bandwidth and read cost are the required amount of data and access number of nodes to restore a failed node, respectively. Here, the repairable linear code ensemble is given by such parameters as the number k of data symbols, the number m of parity symbols, and their degree distributions. We further assume that the code is systematic, and no other constraint is assumed, except possibly that the exact repair could be done by the parity check-sum relation with fully connected n=k+m storages. This enables one to apply the result of this paper directly to any randomly constructed codes with the above parameters, such as linear fountain codes. The final expression of the average repair read cost shows that it is highly dependent on the degree distribution of parity symbols, and also the values n and k.

• Journal of the Korean Society of Combustion
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• v.15 no.3
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• pp.67-73
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• 2010

The temperature distribution of diesel particulate filter with five partitioned electric heaters is numerically analyzed to investigate the condition of regenerating ceramic filter. The commercial code STAR-$CCM+^{(R)}$ is utilized to simulate multi-dimensional steady hot air flow in DPF. In order to verify the computational results, thermocouples are used to measure the temperature distribution in DPF. Computational results agree well with experimental ones. The results show that the maximum temperature in DPF is lowered as the mass flow rate of exhaust gas increases, which means that the more power in heater will be necessary as the engine speed increases. Compared with heater placed at center, heater at circumference has the higher maximum temperature in DPF. The maldistribution of flow field in front of heater has the main influence on the temperature distribution in DPF.

• Transactions on Electrical and Electronic Materials
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• v.11 no.5
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• pp.226-229
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• 2010

Many methods exist that promote wound healing, including light therapy, which consists of light beams that assist the human body in treating and sterilizing wounds, as well as regenerating cells. Irradiation with specific wavelengths of either laser or LED light has been shown to induce beneficial proliferation of fibroblasts that, depending on the size of the wound, can be effective in promoting wound healing. The experiments in this study utilized 8 week old 250~300 g Male Sprague Dawley Rats (ILAR Code: NTacSam:SD) and included a non-irradiation group and a 525 nm green LED irradiation group (n of each group = 7). In experiments animals were allowed to rest for 24 hours after wounds had been excised, which was followed by non- irradiation or 525 nm green LED irradiation therapy one hour per day for 9 days. Immunohistochemical staining was conducted for cytokeratin in order to precisely measure the defect size. In addition, Masson's trichrome staining was utilized in order to compare levels of collagen between the 525 nm green LED irradiation group and the non-irradiation group. Animals exposed to 525 nm green LED irradiation (p<0.05) healed at a faster rate and had increased collagenosis compared with the non-irradiated control group. Thus, treatment with 525 nm green LED irradiation had a beneficial effect on wound healing and should be considered as a possible alternative to low power laser treatment.