• Journal of the Korea Society of Computer and Information
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• v.28 no.8
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• pp.1-10
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• 2023

Recently, NAND flash memories have replaced magnetic disks due to non-volatility, high capacity and high resistance, in various computer systems but it has disadvantages which are the limited lifespan and imbalanced operation latency. Therefore, many page replacement policies have been studied to overcome the disadvantages of NAND flash memories. Although it is clear that these policies reflect execution characteristics of various environments and applications, researches on the foundation-policy decision for disk buffer management are insufficient. Thus, in this paper, we propose a foundation-policy recommendation model, called FRM for effectively utilizing NAND flash memories. FRM proposes a suitable page replacement policy by classifying and analyzing characteristics of workloads through machine learning. As an implementation case, we introduce FRM with a disk buffer management policy and in experiment results, prediction accuracy and weighted average of FRM shows 92.85% and 88.97%, by training dataset and validation dataset for foundation disk buffer management policy, respectively.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1095-1102
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• 2023

Content Centric Network (CCN) is a network that emerged to improve the existing network structure and communicates based on content names instead of addresses. It utilises caches to distribute traffic and reduce response time by delivering content from intermediate nodes. In this paper, we propose a popularity-based caching policy to efficiently utilise the limited CS space in CCN environment. The performance of CCNs can vary significantly depending on which content is prioritised to be stored and released. To achieve the most efficient cache replacement, we propose a real-time content popularity-based efficient cache replacement policy that calculates and prioritises content popularity based on constructor popularity, constructor distance, and content hits, and demonstrate the effectiveness of the new policy through experiments.

• Journal of Chest Surgery
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• v.37 no.4
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• pp.328-334
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• 2004

There are only limited numbers of reports about long-term results of tricuspid valve replacement(TVR) with bioprosthetic and mechanical prostheses. We analyzed risk factors for tricuspid valve replacement and compared long-term clinical results of bioprosthetic and mechanical valves in tricuspid position. Material and Method: We reviewed 77 cases of TVR, which were performed between October 1978 and December 1996. Mean age was 38.8 15.9 years. Bioprostheses were implanted in 26 cases and mechanical prostheses were implanted in 51 cases. Result The operative mortality was 15.6% and late mortality was 12.3%. Survival for bioprosthetic and mechanical valve group at 5, 10 and 13 years was 81.3% vs. 100%, 66.1% vs. 100%, 60.6% vs. 100% (p=0.0175). Free from valve related re-operation for bioprosthetic and mechanical valve group at 5, 10 and 13 years was 100% vs. 93.9%, 100% vs. 93.9% and 58.3% vs. 93.9% (p=0.3274). Linealized incidences of valve related re-operation for bioprosthetic and mechanical valve group was 2.27 %/patient-years and 1.10 %/patient-years. Risk factor analysis showed that presence of preoperative ascites, hepatomegaly larger than 2 finger breaths, poor preoperative NYHA functional class and number of tricuspid valve replacement were risk factors for early mortality, and the use of bioprosthetic valve and number of open heart surgery were risk factors for late mortality. Conclusion: Long-term survival of mechanical valve was superior to bioprosthetic valve in tricuspid position. We recommend mechanical valve in tricuspid position if the patient can be closely followed up.

• The Journal of Society for e-Business Studies
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• v.12 no.3
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• pp.211-234
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• 2007

In e-business, XML is a major format of data and it is essential to efficiently process queries against XML data. XML query caching has received much attention for query performance improvement. In employing XML query caching, some efficient technique of cache replacement is required. The previous techniques considered as a replacement unit either the whole query result or the path in the query result. The former is simple to employ but it is not efficient whereas the latter is more efficient and yet the size difference among the potential victims is large, and thus, efficiency of caching would be limited. In this paper, we propose a new technique where the element in the query result is are placement unit to overcome the limitations of the previous techniques. The proposed technique could enhance the cache efficiency to a great extent because it would not pick a victim whose size is too large to store a new cached item, the variance in the size of victims would be small, and the unused space of the cache storage would be small. A technique of XML semantic cache replacement is presented which is based on the replacement function that takes into account cache hit ratio, last access time, fetch time, size of XML semantic region, size of element in XML semantic region, etc. We implemented a prototype XML semantic cache system that employs the proposed technique, and conducted a detailed set of experiments over a LAN environment. The experimental results showed that our proposed technique outperformed the previous ones.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.115-125
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• 2015

This study investigated the fluidity, heat of hydration, setting time, strength development, and characteristics of hydration and pozzolanic reactions of high-strength high-volume ground granulated blast-furnace slag(GGBFS) blended cement pasts with the water-to-binder ratio of 20% by experiments, and analyzed the effects of the replacement ratio and fineness of GGBFS on the hydration and pozzolanic reaction. The results show that, in the high-strength mixtures with low water-to-binder ratio, the initial hydration is accelerated due to the "dilution effect" which means that the free water to react with cement increases by the replacement of cement by GGBFS, and thus, strengths at from 3 to 28 days were higher than those of plain mixtures with ordinary Portland cement only. Whereas it was found that the long term strength development is limited because the hydration reaction rates rapidly decreases with ages and the degree of pozzolanic reaction is lowered due to insufficient supply of calcium hydroxide according to large replacement of cement by GGBFS. Also, the GGBFS with higher fineness absorbs more free water, and thus it decreases the fluidity, the degree of hydration, and strength. These results are different with those of normal strength concrete, and therefore, should be verified for concrete mixtures. Also, to develop the high-strength concrete with high-volume of GGBFS, the future research to enhance the long-term strength development is needed.

• Resources Recycling
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• v.33 no.3
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• pp.12-20
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• 2024

The global cement industry emits approximately 2.9 billion tons of greenhouse gases, of which 1.74-1.89 billion tons are emitted from limestone, which is the main raw material for clinkers. Therefore, the feasibility of using slag, a non-carbonated CaO-based raw material, must be investigated, and the physical properties of cement must be considered. In this study, the mixing ratios of the raw mix and properties of cement were analyzed. The CaCO₃ replacement ratio was limited when one type of slag was used; however, when the mixed slag was utilized, the CaCO₃ replacement ratio increased by more than 12 %. The compressive strength of the slag-incorporated cement was lower than that of Ordinary Portland Cement (OPC). Therefore, the lime saturation factor (LSF) of the raw mix and fineness of the cement were increased to improve the compressive strength. The compressive strength of cement with improved fineness was similar to that of OPC for a CaCO₃ replacement ratio of up to 6 %, and it decreased as the CaCO₃ replacement ratio was increased to 9 %. When both fineness and LSF were increased, the compressive strength and flow value of the cement with a CaCO₃ replacement ratio of 12 % were similar to that of OPC.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
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• v.16
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• pp.183-203
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• 2001

To accomplish international electronic commerce via the Internet, the most serious dilemma is the international payment system. The BBL is a secure and effective electronic commerce framework for the replacement of traditional paper documents by electronic messages via the Internet providing significant benefits in terms of cost savings, improved logistics and reduced errors in documentation. The most important legal obstacles in the BBL are how to secure authenticity, non-repudiation and message integrity as well as the status of negotiability equivalent to paper B/L. These kinds of functions may be carried out through the electronic title registry of the Bolero International Limited. The technical structure is supported contractually by the Bolero Rulebook. And other documents except B/L can be made out without any legal or technical problems. What are the handicaps of the BBL in its practical use at this time? I can summarize the current and expected problems as follows: First, the fee to join Bolero Association Limited is burdensome to sellers, buyers and trade related organizations all over the world. Second, the liability in errors or defaults in operating central data registry of Bolero International Limited is limited to U.S.$100,000. The amount is not sufficient to the many bulk cargo owners to cover the damages. Third, businessmen are used to traditional paper documents; therefore it takes much time for them to change their customs and practices. So the BBL and traditional papers would be used simultaneously for the time being. Finally, it is very important to incorporate the Rulebook, a multilateral contract binding on all users signed, in each domestic law, which will accomplish the uniform law basis.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.908-911
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• 2004

There are various researches on mobile robot systems. Connection method between server and client of mobile robot system is one of them. In the case of mobile robot system, when connection method between server and client is wireless than wire, applications may be expanded. Also in remote monitoring environment using mobile robot system, we are interested in an effective transmission of the image information between server and client. In this paper, Bluetooth is used for connection method between server and client. One of the major applications of Bluetooth is the cable replacement for mobile and peripheral devices. Using Bluetooth, we propose the control method of mobile robot system. Bluetooth offers fast and reliable transmissions of both voice and data over the globally available 2.4GHz ISM (Industrial, Scientific and Medical) band. It has the advantage of small size, low power and low cost. It has the disadvantage of limited range and limited bandwidth. Also in order to transfer effectively image information between remote site(server) and mobile robot system(client) using Bluetooth, we applied to MPEG-2 and MPEG-4 image compression techniques and the results are compared with each other.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.20-21
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• 2008

In the IEEE 802.16 Wireless MAN standard, the best effort service class is ranked on the lowest position in priority so that only scarce resource may be available for it. Also, the best effort service is usually assisted by a MAC scheme based on reservation ALOHA without explicit acknowledgement. However, the standard only specifies the skeleton of the MAC scheme. In this paper, we propose some rules to specify the indefinite part of the MAC scheme as well as to improve the throughput and delay performance of the MAC scheme. As generic rules for demanding and granting resource, we first propose non-gated exhaustive, gated exhaustive, non-gated limited, and gated limited demand rules, and deficient and full grant rules. Secondly, we propose grant regulation rules, identified as replacement and lifetime rules, to avoid excessive grant incurred by not giving acknowledgement. Noting the residual resource is inflated by adopting a grant regulation rule, we finally propose a rule for investing the residual resource to a subscriber station. Simulation results confirm that a combination of proposed rules improves the performance of the MAC scheme.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.3
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• pp.151-160
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• 2018

NAND flash memories have the advantages of fast access speed, high density and low power consumption, thus they have increasing demand in embedded system and mobile environment. Despite the low power and fast speed gains of NAND flash memory, DRAM disk buffers were used because of the performance load and limited durability of NAND flash cell. However, DRAM disk buffers are not suitable for limited energy environments due to their high static energy consumption. In this paper, we propose WAP-LRU (Write pattern Analysis based Placement by LRU) hybrid disk buffer management policy. Our policy designates the buffer location in the hybrid memory by analyzing write pattern of the workloads to check the continuity of the page operations. In our simulation, WAP-LRU increased the lifetime of NAND flash memory by reducing the number of garbage collections by 63.1% on average. In addition, energy consumption is reduced by an average of 53.4% compared to DRAM disk buffers.