• Geomechanics and Engineering
• /
• 제15권1호
• /
• pp.659-668
• /
• 2018

A series of direct shear tests were implemented on three different types of specimens (i.e., clean Perth sand, sand containing 10, 20 and 30% bentonite, sand containing 1, 3 and 5% slag, and sand containing 10, 20 and 30% bentonite with increasing percentages of added slag (1%, 3% and 5%). This paper focuses on the shear stress characteristics of clean sand and sand mixtures. The samples were tested under different three normal stresses (100, 150 and 200 kPa) and three curing periods of no curing time, 7 and 14 days. It was observed that the shear stresses of clean sand and mixtures were increased with increasing normal stresses. In addition, the use of slag has improved the shear strength of the sand-slag mixtures; the shear stresses rose from 128.642 kPa in the clean sand at normal stress of 200 kPa to 146.89 kPa, 154 kPa and 161.14 kPa when sand was mixed with 1%, 3% and 5% slag respectively and tested at the same normal stress. Internal friction angle increased from $32.74^{\circ}$ in the clean sand to $34.87^{\circ}$, $37.12^{\circ}$ and $39.4^{\circ}$ when sand was mixed with 1%, 3% and 5% slag respectively and tested at 100, 150, and 200 kPa normal stresses. The cohesion of sand-bentonite mixtures increased from 3.34 kPa in 10% bentonite to 22.9 kPa, 70.6 kPa when sand was mixed with 20% and 30% bentonite respectively. All the mixtures of clean sand, different bentonite and slag contents showed different behaviour; some mixtures exhibited shear stress more than clean sand whereas others showed less than clean sand. The internal friction angle increased, and cohesion decreased with increasing curing time.

• Smart Structures and Systems
• /
• 제19권5호
• /
• pp.487-497
• /
• 2017

Semi-active devices use the building's own motion to produce resistive forces and are thus strictly dissipative and require little power. Devices that independently control the binary open/closed valve state can enable novel device hysteresis loops that were not previously possible. However, some device hysteresis loops cannot be obtained without active analog valve control allowing slower, controlled release of stored energy, and is presents an ongoing limitation in obtaining the full range of possibilities offered by these devices. This in silico study develops a proportional-derivative feedback control law using a validated nonlinear device model to track an ideal diamond-shaped force-displacement response profile using active analog valve control. It is validated by comparison to the ideal shape for both sinusoidal and random seismic input motions. Structural application specific spectral analysis compares the performance for the non-linear, actively controlled case to those obtained with an ideal, linear model to validate that the potential performance will be retained when considering realistic nonlinear behaviour and the designed valve control approach. Results show tracking of the device force-displacement loop to within 3-5% of the desired ideal curve. Valve delay, rather than control law design, is the primary limiting factor, and analysis indicates a ratio of valve delay to structural period must be 1/10 or smaller to ensure adequate tracking, relating valve performance to structural period and overall device performance under control. Overall, the results show that active analog feedback control of energy release in these devices can significantly increase the range of resetable, valve-controlled semi-active device performance and hysteresis loops, in turn increasing their performance envelop and application space.

• Asian Pacific Journal of Cancer Prevention
• /
• 제14권5호
• /
• pp.3269-3274
• /
• 2013

Background: The aim was to determine the lifestyle behaviors and the practices for early diagnosis of cancer of cancer patients. Materials and Methods: A descriptive cross-sectional design was used for this study. The sample consisted of 222 patients with a diagnosis of cancer (non-random sample method). Ethical permission was obtained of the Non-interventional Research Ethics Committee of our Institution. Values of p<0.05 were accepted as statistically significant. Results: It was observed that 54.4% of the patients had never performed breast self-examination, 60.8% had never had a mammography, and 71.2% had never had a Pap smear. Sixty-six point two percent of patients had never had screening for colon cancer within the past ten years. GIS cancers were higher in smokers and ex-smokers (p=0.005), in drinkers and in ex-drinkers (p=0.000). The breast cancer rate was higher in obese people (p=0.019). Conclusions: The results of this study provide information on the healthy lifestyle behavior of cancer patients before their diagnosis, and their use of early diagnosis practices. The important aspect of this study is to extend cancer patients' period of life after the diagnosis and treatment process, to make them conscious of risky lifestyle and nutritional behavior so that they can maintain a high quality of life, and to start initiatives in this direction that would ensure changes in behavior.

• Korean Membrane Journal
• /
• 제8권1호
• /
• pp.1-12
• /
• 2006

In semiconductor industries, dissolved oxygen is one of the most undesirable contaminants of ultrapure water. A method for dissolved oxygen removal (DOR) consists in the use of polymeric hollow fibres, loaded with a catalyst and fed with a reducing agent such as hydrogen. In this work, PVDF hollow fibres loaded with Pd were characterized by means of perporometry, scanning electron microscopy (SEM), energy dispersive X-ray (EDX). The hollow fibre analyzed shows a five-layer structure with remarkable morphological differences. An estimation of pore diameters and their distribution was performed giving a mean pore diameter of 100 nm. The permeance and selectivity of the fibres were measured using $H_2,\;N_2,\;O_2$ as single gases, at different operating conditions. An $H_2$ permeance of $37 mmol/m^2s$ was measured and $H_2/O_2$ and $H_2/N_2$ selectivities of ca. 3 were obtained. $H_2$ permeance was 1/3 when a water stream flows in the shell side. Catalytic fibrebehaviour was simulated using a mathematical model for a loop membrane reactor, considering only $O_2$ and $H_2$ diffusive transport inside the membrane and their catalytic reaction. Dimensionless parameters such as the Thiele modulus are employed to describe the system behaviour. The model agrees well with the experimental reaction data.

• 한국치위생학회지
• /
• 제16권1호
• /
• pp.147-153
• /
• 2016

Objectives: The purpose of the study is to investigate the relationship between fluorine concentration within finger nails and the level of dentifrice in dental hygiene students and non-health majoring students. Methods: A self-reported questionnaire was completed by seventy female college students living in Daegu and Gyeongbuk that are not supplied with fluoridation from May to June, 2014. Informed consent was approved by institutional review board (IRB). The questionnaire consisted of general characteristics of the subjects (11 items) and oral health behavior including number of toothbrushing, duration of toothbrushing, number of mouth rinsing, and amount of dentifrice. A dentist and a dental hygienist examined directly the subjects by the guideline of World Health Organization (WHO). The oral examination included decayed tooth, healthy tooth, and filled tooth. The nail samples were obtained from seventy female students. Results: Comparing the dental hygiene students and non-health majoring students, 62.5% of dental hygiene students used approximately 1300mg of dentifrice and 55.2% of non-health majoring students used 1800mg or more of dentifrice. The non-health majoring students used more dentifrice (p<0.01). The fluorine concentration within nails was $1.9905{\mu}l/g$ in dental hygiene students and $3.2149{\mu}l/g$ in non-health majoring students. The fluorine concentration within nails in the dental hygiene students was significantly lower(p<0.01). Conclusions: The accumulation of fluoride in human body is not fully caused by dentifrice. However, The accumulation may occur due to toothbrushing so that it is necessary to educate the students about the right use of the dentifrice.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제13권12호
• /
• pp.6214-6242
• /
• 2019

Routing in mobile ad hoc networks is performed in a distributed fashion where each node acts as host and router, such that it forwards incoming packets for others without relying on a dedicated router. Nodes are mostly resource constraint and the users are usually inclined to conserve their resources and exhibit selfish behaviour by not contributing in the routing process. The trust and reputation models have been proposed to motivate selfish nodes for cooperation in the packet forwarding process. Nodes having bad trust or reputation are detected and secluded from the network, eventually. However, due to the lack of proper identity management and use of non-persistent identities in ad hoc networks, malicious nodes can pose various threats to these methods. For example, a malicious node can discard the bad reputed identity and enter into the system with another identity afresh, called whitewashing. Similarly, a malicious node may create more than one identity, called Sybil attack, for self-promotion, defame other nodes, and broadcast fake recommendations in the network. These identity-based attacks disrupt the overall detection of the reputation systems. In this paper, we propose a reputation-based scheme that detects selfish nodes and deters identity attacks. We address the issue in such a way that, for normal selfish nodes, it will become no longer advantageous to carry out a whitewash. Sybil attackers are also discouraged (i.e., on a single battery, they may create fewer identities). We design and analyse our rationale via game theory and evaluate our proposed reputation system using NS-2 simulator. The results obtained from the simulation demonstrate that our proposed technique considerably diminishes the throughput and utility of selfish nodes with a single identity and selfish nodes with multiple identities when compared to the benchmark scheme.

• 한국지반공학회논문집
• /
• 제20권3호
• /
• pp.97-106
• /
• 2004

토피고가 낮아 지반의 자립성이 적은 토사층, 풍화암층에서 시공되는 터널 구조물의 경우, 시공중 붕락을 방지하고 단기적인 안정성을 확보하기 위해서 보조공법들이 사용되는데 특히, 터널의 보강과 차수효과를 동시에 얻을 수 있는 강관 다단 그라우팅 공법(Umbrella Arch Method)이 많이 적용되고 있다. 그러나, 국내에서는 아직 본 공법의 적용에 있어 외국자료나 경험적 방법에 의한 설계 및 시공이 이루어지고 있는 실정임을 감안할 때, 합리적이고 이론적인 설계 및 해석기법의 도입이 필요하다. 본 논문에서는 강관 다단 그라우팅 공법을 적용한 NATM 현장에서 계측을 통해 터널 굴착에 따른 강관의 거동을 분석하고, UAM 설계시에 적용할 수 있는 하중계를 제안하였다. 그리고, 제안된 하중계를 바탕으로 실제 현장에서 적용할 수 있는 UAM의 설계지침 즉, 강관길이$(L_e , L_b)$, 중첩시공거리(x), 횡방향 설치간격 등을 결정할 수 있는 설계법을 제안하였다.

• 한국건설순환자원학회논문집
• /
• 제4권4호
• /
• pp.454-462
• /
• 2016

지오폴리머 콘크리트는 콘크리트 생산과정에서 발생하는 이산화탄소 배출을 감소시킬 수 있는 대안의 하나로 고려되는 새로운 건설재료이다. 지오폴리머 콘크리트의 재료 개발 및 재료 특성 연구는 많이 진행되고 있으나, 이의 구조부재 적용에 대한 연구는 미흡한 실정이다. 이 논문은 지오폴리머 콘크리트에 매입된 철근의 부착특성에 대한 것으로 압축강도 수준 20, 30 및 40MPa 지오폴리머 콘크리트에 대하여 공칭지름 10,16 및 25mm 철근을 매입한 실험체에 대한 연구를 수행하였다. 총 27개의 시험체를 제작하여 EN10080의 규정에 따라 부착강도 및 부착-슬립 관계를 계측한 내용을 정리한 것이다. 실험결과에 따르면, 압축강도 증가에 따라 부착강도가 증가하는 것을 확인하였고, 일반 콘크리트와 유사하게 철근의 지름이 증가함에 따라 부착강도는 감소하였다. 또한, 이 실험의 결과에 근거하여 지오폴리머 콘크리트에 매입된 철근의 기본 정착길이 산정식을 제안하였다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2001년도 가을 학술발표회 논문집
• /
• pp.29-62
• /
• 2001

Based on the results from investigation of behaviour of pulverized fly ashes (PFA) at laboratory and field, the way how to reduce the environmental impacts to geotechnical practices Is considered and described. In order to reduce discharged industrial by-products, it should primarily be emphasized that an effort are made as much as possible not to put into homing. Secondarily, an effort must be made to increase amount of utilization to geotechnical engineering practices. In addition, from an environmental point of view, we should challenge to create innovative materials which are eligible for controlling other wastes and remedying contamination m soils by using industrial byproducts which belong to wastes This Is a new concept in which the polluting materials can be eliminated by making use of wastes. Based on the above-stated concept, the previous and possible utilization of PFA is classified into: (1 ) reclamation, embankment or backfill material, (2) light weight geo-material, (8) soil stabilization/improvement, and (4) environmental material. The reason why PFA, in particular, slurry PFA has been used and will possibly be used more widely is due to the fact that PFA has the advantages : (i) low specific gravity leading to a light weight geomaterial, (ii) high pozzolanic activity enhancing strength, especially due to cement addition, and (iii) spherical shape of particles producing isotropy and then pumpability. As well as the concept of reducing geo-environmental impacts, the present text mainly describes the successful results at laboratory and field which have been obtained by the authors. The most important issue hi application of byproducts including PFA for geotechnical practices is to prevent leakage of polluted substances from sedimentary deposits, ground and earth structures. As one of possible techniques far achieving this purpose, a method of washing off the polluted substances by hot water is described.

• Computers and Concrete
• /
• 제2권1호
• /
• pp.31-53
• /
• 2005

In the present structural codes the safety verification is based on a linear analysis of the structure and the satisfaction of ultimate and serviceability limit states, using a semi-probabilistic security format through the consideration of partial safety factors, which affect the action values and the characteristic values of the material properties. In this context, if a non-linear structural analysis is wanted a difficulty arises, because the global safety coefficient, which could be obtained in a straightforward way from the non-linear analysis, is not directly relatable to the different safety coefficient values usually used for the different materials, as is the case for reinforced concrete structures. The work here presented aims to overcome this difficulty by proposing a methodology that generalises the format of safety verification based on partial safety factors, well established in structural codes within the scope of linear analysis, for cases where non-linear analysis is needed. The methodology preserves the principal assumptions made in the codes as well as a reasonable simplicity in its use, including a realistic definition of the material properties and the structural behaviour, and it is based on the evaluation of a global safety coefficient. Some examples are presented aiming to clarify and synthesise all the options that were taken in the application of the proposed methodology, namely how to transpose the force distributions obtained with a non-linear analysis into design force distributions. One of the most important features of the proposed methodology, the ability for comparing the simplified procedures for second order effects evaluation prescribed in the structural codes, is also presented in a simple and systematic way. The potential of the methodology for the development and assessment of alternative and more accurate procedures to those already established in codes of practice, where non-linear effects must be considered, is also indicated.