• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.12
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• pp.5375-5400
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• 2016

IOMMU is a hardware unit that is indispensable for DMA. Besides address translation and remapping, it also provides I/O virtual address space isolation among devices and memory access control on DMA transactions. However, currently commodity virtualization platforms lack of IOMMU virtualization, so that the virtual machines are vulnerable to DMA security threats. Previous works focus only on DMA security problem of directly assigned devices. Moreover, these solutions either introduce significant overhead or require modifications on the guest OS to optimize performance, and none can achieve high I/O efficiency and good compatibility with the guest OS simultaneously, which are both necessary for production environments. However, for simulated virtual devices the DMA security problem also exists, and previous works cannot solve this problem. The reason behind that is IOMMU circuits on the host do not work for this kind of devices as DMA operations of which are simulated by memory copy of CPU. Motivated by the above observations, we propose an IOMMU para-virtualization solution called PVIOMMU, which provides general functionalities especially DMA security guarantees for both directly assigned devices and simulated devices. The prototype of PVIOMMU is implemented in Qemu/KVM based on the virtio framework and can be dynamically loaded into guest kernel as a module, As a result, modifying and rebuilding guest kernel are not required. In addition, the device model of Qemu is revised to implement DMA access control by separating the device simulator from the address space of the guest virtual machine. Experimental evaluations on three kinds of network devices including Intel I210 (1Gbps), simulated E1000 (1Gbps) and IB ConnectX-3 (40Gbps) show that, PVIOMMU introduces little overhead on DMA transactions, and in general the network I/O performance is close to that in the native KVM implementation without IOMMU virtualization.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.2
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• pp.133-138
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• 2001

In this study, an attempt was made to increase the survival rate of bifidobacteria entrapped in alginate in the gastrointestinal tract, and to investigate the potential industrial applications, for example lyophilized capsules and yogurt. First, the protective effect of various food additives on bifidobacterial survivability was determined after exposure to simulated gastric juices and bile salts. The additives used in this study were skim milk (SM), polydextrose (PD), soy fiber (SF), yeast extract (YE), chitosan (CS), $\kappa$-carageenan ($\kappa$-C) and whey, which were added at 0.6% concentration (w/v) to 3% alginate-bifidobacterial solution. In the simulated gastric juices and bile salts, the protective effect of 0.6% skim milk-3% alginate (SM-A) beads on the survival rate of bifidobacteria proved to be higher than the other additives. Second, the hydrogen ion permeation was detected through SM-A vessel without bifidobacterial cells at different SM concentrations (0.2%, 0.4%, 0.6%, 0.8%, and 1.0%). There were no differences in terms of the pH decrease in SM-A vessels at 0.6%, 0.8%, and 1.0% (w/v) SM concentrations. The survival rate of bifidobacteria in SM-A beads would appear to be related to the SM buffering capacity against hydrogen ions and its tendency to reduce the pore size of bead. In this experiment, the survival rate of bifidobacteria entrapped in beads containing 0.6% SM showed the highest viability after exposure to simulated gastric juices for 3h, thereby indicating that 0.6% SM is the optimum concentration fir 3% alginate bead preparation. Third, the effect of SM-A beads on the freeze-drying and yogurt storage for 10 days was investigated. SM-A beads were found to be more efficient for freeze drying and yogurt storage than untrapped cells and the alginate bead. Consequently, the survival rate of bifidobacteria entrapped in SM-A beads was increased in simulated gastric juices, bile salts and probiotic products, such as lyophilized capsules and yogurt, SM-A beads can be expected to produce high value probiotic products.

• Journal of Microbiology and Biotechnology
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• v.29 no.2
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• pp.200-208
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• 2019

Probiotics show low cell viability after oral administration because they have difficulty surviving in the stomach due to low pH and enzymes. For the oral delivery of probiotics, developing a formula that protects the probiotic bacteria from gastric acidity while providing living cells is mandatory. In this study, we developed tablets using a new pH-sensitive phthalyl inulin (PI) to protect probiotics from gastric conditions and investigated the effects of different compression forces on cell survival. We made three different tablets under different compression forces and measured survivability, disintegration time, and kinetics in simulated gastric-intestinal fluid. During tableting, there were no significant differences in probiotic viability among the different compression forces although disintegration time was affected by the compression force. A higher compression force resulted in higher viability in simulated gastric fluid. The swelling degree of the PI tablets in simulated intestinal fluid was higher than that of the tablets in simulated gastric fluid due to the pH sensitivity of the PI. The probiotic viability formulated in the tablets was also higher in acidic gastric conditions than that for probiotics in solution. Rapid release of the probiotics from the tablet occurred in the simulated intestinal fluid due to the pH sensitivity. After 6 months of refrigeration, the viability of the PI probiotics was kept. Overall, this is the first study to show the pH-sensitive properties of PI and one that may be useful for oral delivery of the probiotics.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.3
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• pp.341-347
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• 2011

The redundancy allocation problem (RAP) is a famous NP.complete problem that has beenstudied in the system reliability area of ships and airplanes. Recently meta-heuristic techniques have been applied in this topic, for example, genetic algorithms, simulated annealing and tabu search. In particular, tabu search (TS) has emerged as an efficient algorithmic approach for the series-parallel RAP. However, the quality of solutions found by TS depends on the initial solution. As a robust and efficient methodology for the series-parallel RAP, the hybrid metaheuristic (TSA) that is a interactive procedure between the TS and SA (simulated annealing) is developed in this paper. In the proposed algorithm, SA is used to find the diversified promising solutions so that TS can re-intensify search for the solutions obtained by the SA. We test the proposed TSA by the existing problems and compare it with the SA and TS algorithm. Computational results show that the TSA algorithm finds the global optimal solutions for all cases and outperforms the existing TS and SA in cases of 42 and 56 subsystems.

• Industrial Engineering and Management Systems
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• v.10 no.2
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• pp.134-139
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• 2011

The problem of scheduling in permutation flowshops has been extensively investigated by many researchers. Recently, attempts are being made to consider more than one objective simultaneously and develop algorithms to obtain a set of Pareto-optimal solutions. Varadharajan et al. (2005) presented a multi-objective simulated-annealing algorithm (MOSA) for the problem of permutation-flowshop scheduling with the objectives of minimizing the makespan and the total flowtime of jobs. The MOSA uses two initial sequences obtained using heuristics, and seeks to obtain non-dominated solutions through the implementation of a probability function, which probabilistically selects the objective of minimizing either the makespan or the total flowtime of jobs. In this paper, the same problem of heuristically developing non-dominated sequences is considered. We propose an effective heuristics based on simulated annealing (SA), in which the weighted sum of the makespan and the total flowtime is used. The essences of the heuristics are in selecting the initial sequence, setting the weight and generating a solution in the search process. Using a benchmark problem provided by Taillard (1993), which was used in the MOSA, these conditions are extracted in a large-scale experiment. The non-dominated sets obtained from the existing algorithms and the proposed heuristics are compared. It was found that the proposed heuristics drastically improved the performance of finding the non-dominated frontier.

• Journal of Ocean Engineering and Technology
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• v.17 no.6
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• pp.38-46
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• 2003

Aim of this article is to propose Micro-Genetic Simulated Annealing (${\mu}GSA$) as a hybrid metaheuristics approach to find the global optimum of nonlinear optimisation problems. This approach combines the features of modern metaheuristics such as micro-genetic algorithm (${\mu}GAs$) and simulated annealing (SA) with the general robustness of parallel exploration and asymptotic convergence, respectively. Therefore, ${\mu}GSA$ approach can help in avoiding the premature convergence and can search for better global solution, because of its wide spread applicability, global perspective and inherent parallelism. For the superior performance of the ${\mu}GSA$, the five well-know benchmark test functions that were tested and compared with the two global optimisation approaches: scatter search (SS) and hybrid scatter genetic tabu (HSGT) approach. A practical application to structural sandwich panel is also examined by optimism the weight function. From the simulation results, it has been concluded that the proposed ${\mu}GSA$ approach is an effective optimisation tool for soloing continuous nonlinear global optimisation problems in suitable computational time frame.

• Journal of Electrical Engineering and Technology
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• v.6 no.4
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• pp.431-438
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• 2011

To ensure that equipment outages do not directly impact the reliability of the ISO-controlled grid, market participants request permission and receive approval for planned outages from the independent system operator (ISO) in competitive electricity markets. In the face of major generation outages, the ISO will make a critical decision as regards the scheduling of the essential maintenance for myriads of generating units over a fixed planning horizon in accordance with security and adequacy assessments. Mainly, we are concerned with a fundamental framework for ISO's maintenance coordination in order to determine precedence of conflicting outages. Simulated annealing, a powerful, general-purpose optimization methodology suitable for real combinatorial search problems, is used. Generally, the ISO will put forward its best effort to adjust individual generator maintenance schedules according to the time preferences of each power generator (GENCO) by taking advantage of several factors such as installed capacity and relative weightings assigned to the GENCOs. Thus, computer testing on a four-GENCO model is conducted to demonstrate the effectiveness of the proposed method and the applicability of the solution scheme to large-scale maintenance scheduling coordination problems.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.629-638
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• 2000

With the positive features of simulated annealing algorithms such as simplicity of the algorithm and the possibility of finding global optimum solution, SA algorithm has been widely applied to structural optimization problems. However, the algorithms are far from practical applications in structural design or optimization of building structures due to requirement of a large number of iterations and dependency on cooling schedule and stopping criteria. In this paper, with the modification of annealing process and stopping criteria, a MSA algorithm is presented in the form of two phase annealing process for optimal seismic design of braced structures. The performance of the proposed algorithm has been illustrated in detail.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.406-409
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• 1999

Experimental Investigations were carried out to remove NOx, SOx simultaneously from simulated flue gas[NO(0.02%)-SO$_2$(0.08%)-$CO_2$-Air-$N_2$] by using a plasma chemical reaction. Ammonia gas(14.81%) balanced by argon was diluted by all and was Introduced to mall simulated flue gas duct through NH$_3$ Injection system which is in downstream of reactor. The NH$_3$ molecular ratio(MR) was determined based on (NH3) to [NO+S0$_2$]. MR is 1, 1.5, 2.5. The NOx removal rate significantly increased with increasing NaOH bubble quantity. The SO$_2$ removal rate was not significantly effected by applied voltage, however it fairly Increased with increasing NH$_3$ molecule ratio. By-product aerosol particle was observed by XRD(X-ray diffraction) after sampling, The NOx, SOx removal rates, when H2O vapour bubbled by dry all was injected to plasma reactor, were better than those of other cases. When aqueous NaOH solution(20%) bubbled by 2.5( ι /min) of $N_2$ and 0.5 ( ι /min) NH$_3$(MR=1.5) were injected to simulated flue gas, The NOx. SOx removal rate was 95 ~ 100[%]

• Nuclear Engineering and Technology
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• v.53 no.4
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• pp.1218-1223
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• 2021

A hydrophobic ionic liquid including an amino moiety ([DiOcAPmim][NTf₂]) was synthesized. Its extraction behaviors towards Pd(II), Ru(III), Rh(III) were investigated in nitric acid aqueous solution as a function of contact time, effect of concentration of nitric acid, effect of temperature, and effect of co-existing metal ions. The extraction kinetics of Pd(II) was fairly fast and extraction equilibrium can be attained within only 5 min under the [HNO₃] = 2.05 M. When [HNO₃]< 1 M, the extraction percentage of Pd(II), Ru(III), Rh(III) were all above 80%. When [HNO₃] reached 2 M, all of the extraction percentage decreased and in an order of Pd(II)>Ru(III)>Rh(III). When [HNO₃]> 2 M, the extraction performance gradually recovered. The effect of temperature can slightly affect the extraction performance of Pd(II). Furthermore, in simulated high-level liquid waste, [DiOcAPmim][NTf₂] showed a better preference towards Pd(II) under the interference of various other co-existing metal ions.