• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.13-22
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• 2011

In this study, ultimate strengths of 51 continuous reinforced concrete deep beams were evaluated by the ACI 318M-08's strut-tie model approach implemented with the presented indeterminate strut-tie model and load distribution ratio of the companion paper. The ultimate strengths of the continuous deep beams were also estimated by the shear equations derived based on experimental results, conventional design codes based on experimental and theoretical shear strength models, and current strut-tie model design codes. The validity of the presented strut-tie model and load distribution ratio was examined through the comparison of the strength analysis results classified according to the primary design variables of shear span-to-effective depth ratio, flexural reinforcement ratio, and concrete compressive strength. The present study results of ultimate strengths obtained using the indeterminate strut-tie model and load distribution ratio of the continuous deep beams agree fairly well with those obtained using other approaches. In addition, the present approach reflected the effect of the primary design variables on the ultimate strengths of the continuous deep beams consistently and accurately. Therefore, the present study will help structural designers to conduct rational and practical strut-tie model designs of continuous deep beams.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.205-214
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• 2012

Crack widths play an important role in the serviceability limit state. When crack widths are controlled sufficiently, the reinforcement corrosion can be reduced using only existing concrete cover thickness due to low permeability in the region of finely distributed hair-cracks. Thus, the knowledge about the tensile crack opening is essential in designing more durable concrete structures. Therefore, numerous researches related to the topic have been performed. Nevertheless accurate measurement of a crack width is not a simple task due to several reasons such as unknown potential crack formation location and crack opening damaging strain gages. In order to overcome these difficulties and measure precise crack widths, a displacement measurement system was developed using digital image correlation. Accuracy calibration tests gave an average measurement error of 0.069 pixels and a standard deviation of 0.050 pixels. Direct tensile test was performed using ultra high performance concrete specimens. Crack widths at both notched and unnotched locations were measured and compared with clip-in gages at various loading steps to obtain crack opening profile. Tensile deformation characteristics of concrete were well visualized using displacement vectors and full-field displacement contour maps. The proposed technique made it possible to measure crack widths at arbitrary locations, which is difficult with conventional gages such as clip-in gages or displacement transducers.

• Journal of the Korean Electrochemical Society
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• v.23 no.4
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• pp.97-104
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• 2020

One of the main challenges of electrochemical water splitting technology is to develop a high performance, low cost oxygen-evolving electrode capable of substituting a noble metal catalyst, Ir or Ru based catalyst. In this work, CoFe₂O₄ nanoparticles with sub-44 nmsize of a inverse spinel structure for oxygen evolution reaction (OER) were synthesized by the injection of KNO₃ and NaOH solution to a preheated CoSO₄ and Fe(NO₃)₃ solution. The synthesis time of CoFe₂O₄ nanoparticles was controlled to control particle and crystallite size. When the synthesis time was 6 h, CoFe₂O₄ nanoparticles had high conductivity and electrochemical surface area. The overpotential at current denstiy of 10 mA/㎠ and Tafel slope of CoFe₂O₄ (6h) were 395 mV and 52 mV/dec, respectively. In addition, the catalyst showed excellent durability for 18 hours at 10 mA/㎠.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.2
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• pp.208-213
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• 2011

This paper analyzes potential interference effects of Ultra Wide Band(UWB) on Global Positioning System(GPS) which is providing safety service. For the interference analysis, positioning error method is used to determine the minimum protection distance to meet positioning error of 2.5 m below and Minimum Coupling Loss(MCL) method is used to determine the required protection ratio(I/N) from the protection distance of UWB transmitter and GPS receiver to meet positioning error of 2.5 m below. In a result, the minimum protection distance to meet positioning error of 2.5 m below was about 10 m and the protection ratio to meet positioning error 2.5 m below was -20 dB. The protection ratio proposed in this paper is the same value of the protection ratio of safety service proposed by ITU-R. The obtained protection ratio can be used for the protection standard of domestic GPS system for the safe of life service.

• Journal of Periodontal and Implant Science
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• v.31 no.3
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• pp.555-564
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• 2001

The purpose of this study is to evaluate the bioresorbability of Calcium Polyphosphate added with $Na_2O$ and chitosan. Though calcium phosphate ceramics meet some of the needs for bone replacement, they have some limitation of unresorbability and fibrous encapsulation without direct bone apposition during bone remodelling. To solve these problem, we developed a new ceramic, calcium polyphosphate(CPP), and report the biologic response to CPP in extraction sites of beagle dog. Porous CPP granules were prepared by condensation of anhydrous $Ca(H_2PO_4)_2$ to form non-crystalline $Ca(PO_3)_2$. CPP granules added with $Na_2O$ and chitosan were implanted in extraction sockets and histologic observation were performed at 12 weeks later. Histologic observation at 12 weeks revealed that CPP matrix were mingled with and directly apposed to new bone without any intervention of fibrous connective tissue. CPP granules added with chitosan were well adatped without any adverse tissue reaction and resorbed slowly and spontaneously. CPP granules added with $Na_2O$ and chitosan show multinucleated giant cells and osteoblast-like cells around grafted material and newly formed bone. This result revealed that CPP, regardless of its additive component, had a high affinity for bone and had been resorbed slowly. From this results, it was suggested that CPP is promising ceramic as a bone substitute and addition of $Na_2O$ and chitosan help biodegradation. In further study , it will be determined which concentration of $Na_2O$ help biodegradation and the other additive components increase the degradation rate.

• Journal of Periodontal and Implant Science
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• v.32 no.1
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• pp.143-160
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• 2002

타이태늄은 뛰어난 생체적합성과 적절한 물리적 성질을 바탕으로 치과 및 정형외과 영역의 매식재로 널리사용되어져 왔으며, 골과 매식재 사이의 골 융합 정도를 증가시킬 목적으로 물리, 화학적인 방법을 이용한 타이태늄의 표면처리에 관한 많은 연구들이 진행되어 왔다. 최근에는 부착단백질 또는 성장인자를 이용한 생체재료의 표면개질을 통하여 조직적합성 및 치유 능의 개선을 위한 시도들이 있어왔다. Fibronectin(FN)은 주요 세포외기질중의 하나로 생체 내 널리 분포하여 세포의 부착, 이동 및 증식에 관여하는 거대 당단백으로, RGD및 PHSRN 펩타이드 서열이 세포의 인테그린과 결합하여 세포의 활성을 조절하는 것으로 알려져 있다. 이 연구에서는 FN으로 처리된 타이태늄이 조골세포의 부착, 증식 및 분화에 미치는 영향과 이에 따른 석회화 정도에 미치는 영향을 관찰하여 부착분자를 이용한 타이태늄 표면개질의 효과를 규명하고자 하였다. 상업용 순수 타이태늄을 gold thiol법을 이용하여 표면처리 후, 혈장 FN(plasma FN, pFN)과 유전자재조합법을 이용하여 얻은 FN조각(FN type III 7-10, FNIII 7-10)을 피복한 시편을 실험군으로, 아무런 처리를 하지 않은것(smooth surface, SS)과 산 부식(Sandblasted and acid etched, SLA)처리된것을 대조군으로 이용하였다. 배양된 조골세포주(MC3T3-E1)를 사용하여 타이태늄 표면 처리에 따른 세포의 증식, 형태변화, 알칼리성 인산분해효소(ALPase) 생산 및 세포면역형광법을 이용한 분화정도를 시간 경과에 따라 관찰하였다. 조골세포증식의 경우 FNIII 7-10 처리군에서 pFN 처리군 및 대조군에 비해 시간경과에 따라 유의성있는 세포수의 증식이 관찰되었으며(p<0.05), ALPase 생성의 경우에도 FNIII 7-10 처리 군에서 아무 처리도 하지 않은 군에 비해 유의성 있게 높은 효소의 생성이 관찰되었다(p<0.05). 주사전자현미경을 이용한 세포의 형태관찰결과 아무 처리도 하지 않은 군에서는 마름모형태를 나타내었으며, 산 부식 처리된 군에서는 세포가 가시모양의 형태를 보인 반면 FN으로 처리된 두 군에서는 세포의 부착 및 펴짐이 매우 발달되어 있는 모습이 관찰되었다. 세포의 분화정도를 관찰하기 위하여 국소부착키나제(focal adhesion kinase, FAK), 및 actin stress fiber의 분포양상을 세포면역형광법을 이용하여 관찰한 결과 FN으로 표면처리된 두 군에서 아무런 처리도 하지않은 군 및 산 부식처리 한 군에 비해 프라크의 발현이 높게 나타났으며 잘 발달된 actin stress fiber의 소견을 나타내었다. 이 실험의 결과들은 gold thiol 법을 이용한 표면처리 후 FN부착을 통한 타이태늄의 표면개질이 조골세포의 부착, 증식 및 분화에 중요한 역할을 담당하여 석회화 정도를 촉진시키는 것을 보여주었으며, 이런 결과들은 더 짧은 FN조각을 이용한 다른 생체재료의 표면개질에 폭 넓게 응용할 수 있으리라 생각된다.

• Journal of Korean Society of Forest Science
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• v.108 no.4
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• pp.574-581
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• 2019

The present study analyzed the productivity and cost of winching operations for evaluating the efficiency of a tractor-attached winch in a Pinus densiflora thinning site located in the Yangyang County of Gangwon-do. The mean yarding distance and mean timber volume were 29 m and 0.15 ㎥, respectively. In the 95 cycles of yarding operations, the uphill and downhill yarding operations constituted 51% and 49%, respectively, of the total yarding operations. The productivity of the uphill yarding operation was 2.28 ㎥/h, and the productivity of the downhill yarding operation was 1.89 ㎥/h. The findings of this study revealedthat productivity would increase by 0.5 ㎥/h when the rate of utilization of the machine is increased to 80% by reducing the operational delay time. The cost of the downhill yarding operation was 44,116 KRW/㎥, whereas that of the uphill yarding operation was 53,369 KRW/㎥. The difference in cost resulted from the difference in the number of yarding stems (stems/cycle). Furthermore, the results of the multiple linear regression equation developed for predicting the yarding operation times showed that productivity was significantly affected by working conditions such as yarding distance (m), the number of stems per cycle (stems/cycle), and the terrain slope (%) in the uphill and downhill yarding operations. Further research is required for developing an accurate prediction model equation according to a yarding direction.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.5
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• pp.540-548
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• 2012

The Weapon Target Allocation(WTA) problem is the NP-Complete problem. The WTA problem is that the threatful air targets are assigned by weapon of allies for killing the targets. A good solution of NP-complete problem is heuristic algorithms. Genetic algorithms are commonly used heuristic for global optimization, and it is good solution on the diverse problem domain. But there has been very little research done on the generation of their initial population. The initialization of population is one of the GA step, and it decide to initial value of individuals. In this paper, we propose to the population initialization method to improve a Genetic Algorithm. When it initializes population, the proposed algorithm reflects the characteristics of the WTA problem domain, and inherits the dominant gene. In addition, the search space widely spread in the problem space to find efficiently the good quality solution. In this paper, the proposed algorithm to verify performance examine that an analysis of various properties and the experimental results by analyzing the performance compare to other algorithms. The proposed algorithm compared to the other initialization methods and a general genetic algorithm. As a result, the proposed algorithm showed better performance in WTA problem than the other algorithms. In particular, the proposed algorithm is a good way to apply to the variety of situation WTA problem domain, because the proposed algorithm can be applied flexibly to WTA problem by the adjustment of RMI.

• Journal of IKEEE
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• v.9 no.1 s.16
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• pp.19-30
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• 2005

Packet classification is defined as the action to match the packet with a set of predefined rules. One of classification is to use Ternary Content Addressable Memory hardware search engine that has faster than other algorithmic methods. However, TCAM has some limitations. One of them is that TCAM can not perform range matching efficiently. A range has to be expanded into prefixes to fit the boundary. In general, the number of expansion could be up to 2w-2, where w is the width of the field. For example, if two range fields with 16 bits are used, there could be up to $30\;{\times}\;30\;=\;900$ expansions for a single rule. In this paper, we describe the novel algorithm for converting range matching rules into TCAM entry efficiently. The number of maximum entry is 2w-4 when using the algorithm. Furthermore, it has also benefit about the negation range. In the result of experimentation, the new scheme practically reduces 14 percent in case that searched fields are source port and destination port number.

• Korean Journal of Health Education and Promotion
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• v.26 no.4
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• pp.35-47
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• 2009

Objectives: The purpose of this research was to investigate incidence and related factors of the MS in a university hospital Methods: This survey was conducted from January in 1997 to March in 2008. This study is a cohort study. The baseline subjects were 529 men and 609 women without metabolic syndrome(MS) who visited the health promotion center of Chungnam National University Hospital for general health check-up. The MS was diagnosed according to the definition by the NCEP ATP III. The abdominal obesity guidelines for waist circumference applied the Korean Society for the Study of Obesity Guideline Results: The survey exhibited that baseline risk factors that mainly affect odds ratio(OR) of the MS at follow-up were sex, ages, heavy drinking, uric acid and transpeptidase(GGT) in women. Incidence of the MS was 10.6% in total cases, 18.1% in men and 4.0% in women. The risk of the MS was significantly lower in women than men(OR=0.4, 95% confidence interval(CI: 0.2-0.9), significantly higher 50-59 Ages than < 40 ages(OR=3.4, 95% CI: 1.9-6.4), significantly high in women with heavy drinkers(OR=14.3, 95% CI: 1.2-177.5), significantly high in whole, men and women with high uric acid group(whole, OR=2.6, 95% CI: 1.6-4.2. men, OR=2.1, 95% CI: 1.3-3.5. women, OR=14.2, 95% CI: 3.0-68.3) and significantly high in women with high GGT(OR=1.8, 95% CI: 2.4-12.6). Conclusion: Risk factors of incident MS were baseline sex, ages, heavy drinking in women, uric acid and GGT in women. These can be utilized as an important index to determine risk factors of incident MS and will be basic data in part of management, education, countermeasure and selection test of the MS.