• 분석과 대안
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• 제6권1호
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• pp.7-33
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• 2022

본 논문은 통일에 대한 찬성-반대 응답을 바탕으로 수도권(서울, 인천, 경기) 거주 시민의 통일 의식에 연령대별 차이의 양태를 고찰하였다. 기존 연구에서는 통일에 대한 찬성 의견이 연령과 양의 선형관계에 있다고 보고 있다. 하지만 본 연구의 분석 결과에 따르면, 수도권의 통일에 대한 찬성 의견은 연령의 증가와 함께 증가하지만 44세~ 53세 층에서 가장 높은 찬성 비율을 보인 후 점차 감소하는 것으로 나타났다. 통계모형 분석에서 44 ~ 53세층은 참조집단인 24 ~ 33세층에 비해 승산이 2.5배 이상 높았으며, 남성에 대한 여성의 승산은 0.56배로 나타났다. 한편, 연령별 통일 찬성 비율 평균값의 추세선 기울기 기준으로 연령 증가에 따른 통일 찬성 비율 증가 경향은 남성이 여성보다 약 4.3배 더 큰 것으로 나타났다. 남성 청년층(2030)과 중년층(4050) 간의 현저한 통일 찬성 비율의 차이가 수도권 전체 연령대의 통일 찬성 비율 격차에 영향을 미치는 것으로 보인다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.719-724
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• 2001

In this study, wedge splitting tensile test(WST) using dye penetration method was carried out to investigate cracking criterion and fracture characteristics of concrete. For the this purpose, three levels of compressive strength of 180, 300 and 600 kgf/$\textrm{cm}^2$ and five testing age of 1, 3, 7, 14 and 28 days were selected as test variables. The specimen was loaded in a controlled manner and then dye was inserted at the load of 40%, 70% of the presumed peak load and at the load of 90% just after peak load. The fracture process zone was measured at each load step of a specimen. Test results were compared with analytic results by linear elastic fracture mechanics(LEFM) and numerical results through fictitious crack model(FCM) and finite element method(FEM).

• Computers and Concrete
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• 제8권3호
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• pp.357-369
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• 2011

In this study, effect of steel fibers on toughness and some mechanical properties of concrete were investigated. Hooked-end steel fibers were used in concrete samples with three volume fractions (${\nu}_f$) of 0.5%, 0.75% and 1% and for two aspect ratios (l/d) of 45 and 65. Compressive and flexural tensile strength and modulus of elasticity of concrete were determined for cylindrical, cubic and prismatic samples at the age of 7 and 28 days. The stress-strain curves of standard cylindrical specimens were studied to determine the effect of steel fibers on toughness of steel-fiber-reinforced concrete (SFRC). In addition, the relationship between compressive strength and the flexural tensile strength of SFRC were reported. Finally, a simple model was proposed to generate the stress-strain curves for SFRC based on strains corresponding to the peak compressive strength and 60% of peak compressive stress. The proposed model was shown to provide results in good correlation with the experimental results.

• Tuberculosis and Respiratory Diseases
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• 제79권3호
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• pp.121-126
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• 2016

Lung function reportedly declines with age and that this decline is accelerated during disease progression. However, a recent study showed that the decline might peak in the mild and moderate stage. The prognosis of chronic obstructive pulmonary disease (COPD) can be improved if the disease is diagnosed in its early stages, prior to the peak of decline in lung function. This article reviews recent studies on early COPD and the possibility of applying the U.S. Preventive Services Task Force recommendation 2008 and 2015 for early detection of COPD in Korea.

• The Korean Journal of Ecology
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• 제17권3호
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• pp.415-424
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• 1994

Community structure, size and age distribution of tree species of the subalpine Korean fir (Abies koreana) forest at the elevation of 1, 400~1, 700m were strudied in the north-west side of Chonwangbong Peak (1915m) in Mt. Chiri for the purpose of better understanding of the population dynamics of Abies koreana. Eight 20m X 20m permanent quadrats were established in 1991, and trees $\geq$ 2.5cm DBH for all species were marked with numbered aluminum tag, and saplings of Korean fir and Korean pine (Pinus koraiensis) were also tagged with aluminum sheet. These two conifer species comprised more than 60% of the total density and total basal area of the community. Quercus mongolica and Acer pseudo-sieboldianum were subdominats. Oridination study showed that cool temperate species such as Sorbus commixta, Betula costata, Acer tschonoskii and Acer ukurunduense occurred in close association with Abies koreana and Pinus koraiensis. Major tree species, especially Abies koreana and Pinus koraiensis, were well represented in samller size classes, indicating that they were regenerating well. Age distributuion of the Abies koreana and Pinus koraiensis showed that the former has longer physiological longevity than the latter, and that establishment were episodic and varied with sites, which implies the importance of the role of natural and artificial disturbances in this Abies kireana forest.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.531-537
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• 1998

Recently, the pile driving or blasting works are increasingly done in many areas to perform large scale construction projects. The vibrations from these blasting works may affect the properties of concrete, especially young concrete. The purpose of present study is to explore the effects of vibration at early ages on the properties of concrete. To this end, comprehensive experimental study is conducted in the present study. The major test variables are peak particle velocity or vibration velocity and the age at vibration. The compressive strengths and bond strengths are measured for all the specimens at 28days after casting. The duration of vibration is fixed to 30 minutes for all cases. The results indicate that the strength increases for vibration velocity less than about 0.25cm/sec and decreases for vibration velocity larger than 0.5cm/sec. The effect of age at vibration is not pronounced and shows almost similar behavior for the age at vibration of 0 to 12 hours range. The present study provides some important guidelines to control the construction or vehicle vibrations for the concrete at very early ages.

• 한국분말재료학회지
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• 제12권4호
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• pp.303-308
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• 2005

Various kinds of Mg-Zn-Ca base alloys were rapidly quenched via melt spinning process. The meltspun ternary and quaternary alloy ribbons were heat-treated, and then the effects of additional elements on age hardening behavior and phase change of precipitates were investigated using Vickers hardness tester, XRD, and TEM equipped with EDS system. In ternary alloys, age hardening was mostly due to the distribution of $Mg_6Ca_2Zn_3$ and $Mg_2Ca$. The stable phases of precipitates were varied according to the aging temperature and the alloy composition. With the increase of Ca content, $Mg_2Ca$ precipitates were detected more than $Mg_6Ca_2Zn_3$ precipitates. In quaternary alloys, the precipitates taken from Mg-Zn-Ca-Co were identified as new quaternary phase, whereas those taken from Mg-Zn-Ca-Zr as MgZnCa containing Zr. In general, the ternary alloy showed higher peak hardness and thermal stability than the quaternary considering the total amounts of the solutes. It implies that the structure of precipitate should be controlled to have the coherent interface with the Mg matrix.

• Computers and Concrete
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• 제20권5호
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• pp.529-537
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• 2017

Excessively elevated temperature can lead to cracks in prestressed concrete (PC) continuous bridge with box girder on the pier top at cement hydration age. This paper presents a case study for evaluating the behavior of PC box girder during the early hydration age using a two-stage computational model, in the form of computer program ANSYS, namely, 3-D temperature evaluation and determination of mechanical response in PC box girders. A numerical model considering time-dependent wind speed and ambient temperature in ANSYS for tracing the thermal and mechanical response of box girder is developed. The predicted results were compared to show good agreement with the measured data from the PC box girder of the Zhaoshi Bridge in China. Then, based on the validated numerical model three parameters were incorporated to analyze the evolution of the temperature and stress within box girder caused by cement hydration heat. The results of case study indicate that the wind speed can change the degradation history of temperature and stress and reduce peak value of them. The initial casting temperature of concrete is the most significant parameter which controls cracking of PC box girder on pier top at cement hydration age. Increasing the curing temperature is detrimental to prevent cracking.

• Asian-Australasian Journal of Animal Sciences
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• 제2권4호
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• pp.565-570
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• 1989

The influence of age at first calving on the milk production of crossbred dairy cows produced under major dairy cattle crossbreeding projects in Pakistan was studied from the year 1974 to 1980. These animals were bred and raised at the Livestock Production Research Institute, Bahadarnagar (LPRI), Livestock Experiment Station, Karachi (LES) and the University of Agriculture, Faisalabad (UAF). Local Sahiwal (SWL) cattle were crossed with the European breeds, Holstein Friesian (HF) and Jersey (J) at LPRI and UAF. At LES, native Red Sindhi (RS) were crossed with the HF and J breeds. At LES and UAF, the crossbred progeny, thus, produced comprised of halfbreds only while at LPRI 3/4 HF, 3/4 J, 1/4 HF and 1/4 J groups were also available for this study. The average age at first calving was considerably higher among the native breeds. At LES, the RS calved for the first time at an age of approximately 56 months. Corresponding values for SWLs at LPRI and UAF were 44 and 64 months, respectively. The 1/2 HF and 1/2 J crossbreds calved first at the age of approximately 25, 26, 34, 36, 37 and 38 months at LPRI, LES and UAF respectively. For 3/4 HF, 3/4 K, 1/4 HF and 1/4 J groups of LPRI the average age at first calving was 29, 26, 34 and 33 months. Considerable differences in age at first calving between the crossbreds and native breeds were observed. Due to early maturity, the former attained the peak level of milk production in third lactation whereas the latter groups, because of late maturity, reached this level in their fourth lactation. This study suggested that early maturity in Zebu cattle (Box indicus) could be induced through crossbreeding with European cattle (Bos Taurus).

• Childhood Kidney Diseases
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• 제21권2호
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• pp.94-100
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• 2017

Purpose: The American Academy of Pediatrics provides guidelines for managing febrile urinary tract infection (UTI) in infants and children 2-24 months old, but little guidance is offered regarding UTIs in those younger than 8 weeks of age. The definition of UTI is unclear and whether to proceed with micturating cystourethrography (MCUG) or $^{99m}$technetium-dimercaptosuccinic acid (DMSA) scintigraphy scan in this age group is controversial. Methods: We retrospectively analyzed 29 neonates and infants younger than 2 months of age who underwent late DMSA scans 9 months following the first episode of febrile or symptomatic UTI between July 2009 and June 2016. Results: In total, 192 children aged 0-24 months underwent ultrasound and DMSA scans (MCUG in 174/192). Neonates and infants younger than 2 months of age were significantly less likely to develop fever, and had a lower fever peak, shorter duration of fever before admission and after starting antibiotics, longer hospitalization period, lower C-reactive protein, and greater incidence of nonEscherichia coli infection. There was no difference in pyuria response at diagnosis. The prevalence rates of an ultrasound abnormality (28%), vesicoureteral reflux (28%), UTI recurrence (38%), and renal scarring (10%) in infants younger than 8 weeks of age were similar to those in children 2-24 months old. Conclusion: Neonates and infants younger than 2 months of age with UTI warrant special consideration because the fever response used for diagnosis in older children may be absent or blunted. Clinical guideline is needed for the diagnosis and management of UTI in this age group.