• 지질공학
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• 제9권2호
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• pp.135-145
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• 1999

동적 하중을 받는 지반반응 평가시 필요한 가장 중요한 변수 중에 하나가 지반의 전단탄성계수(G)이다. 지반의 동특성은 시간에 따라 변화하게 되는데, 이 점은 흔히 간과되어져 왔다. 이번 연구를 통하여 일정구속압에서 시간에 따라 변하는 토질 최대전단탄성계수($G_{max}$) 및 그 영향요소에 관해 고찰해보고 몇몇 경험식을 제안하고자 한다. 경험식 작성을 위해 고려된 요소는 선행응력과 선행변형율, 입자크기와 지속응력, 소성지수 등이고, 실제로 가장 큰 영향을 미치는 평균입자직경과 소성지수를 이용한 두개의 경험식을 작성하였다. 끝으로 $G_{max}$의 일시적 변화와 그 원인, 그리고 시간에 따라 증가하는 G가 시사하는 점에 대해 서술한다

• International Journal of Concrete Structures and Materials
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• 제11권1호
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• pp.115-133
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• 2017

To investigate the effectiveness of using fiber reinforced polymer (FRP) sheets in confining heat-damaged columns, 15 circular RC column specimens were tested under axial compression. The effects of heating duration, stiffness and thickness of the FRP wrapping sheets were examined. Two specimen groups, six each, were subjected to elevated temperatures of $500^{\circ}C$ for 2 and 3 h, respectively. Eight of the heat-damaged specimens were wrapped with unidirectional carbon and glass FRP sheets. Test results confirmed that elevated temperatures adversely affect the axial load resistance and stiffness of the columns while increasing their ductility and toughness. Full wrapping with FRP sheets increased the axial load capacity and toughness of the damaged columns. A single layer of the carbon sheets managed to restore the original axial resistance of the columns heated for 2 h yet, two layers were needed to restore the axial resistance of columns heated for 3 h. Glass FRP sheets were found to be less effective; using two layers of glass sheets managed to restore the axial load carrying capacity of columns heated for 2 h only. Confining the heat-damaged columns with FRP circumferential wraps failed in recovering the original axial stiffness of the columns. Test results confirmed that FRP-confining models adopted by international design guidelines should address the increased confinement efficiency in heat-damaged circular RC columns.

• Current Optics and Photonics
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• 제5권3호
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• pp.250-260
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• 2021

A tapered As₂S₃ photonic crystal fiber (PCF) with four layers of air holes in a hexagonal array around the core is designed in this paper. Numerical simulation shows that the dispersion D decreases and the nonlinearity coefficient γ increases from the thick to the thin end along the tapered PCF. We simulate the midinfrared pulse compression in the tapered As₂S₃ PCF using the adaptive split-step Fourier method. Initial Gaussian pulses of 4.4 ps and a central wavelength of 2.5 ㎛ propagating in the tapered PCF are located in the anomalous dispersion region. With an average power of assumed input pulses at 3 mW and a repetition frequency of 81.0 MHz, we theoretically obtain a pulse duration of 56 fs and a compression factor of 78 when the pulse propagates from the thick end to the thin end of the tapered PCF. When confinement loss in the tapered PCF is included in the simulation, the minimum pulse duration reaches 72 fs; correspondingly, the maximum compression factor reaches 61. The results show that in the anomalous-dispersion region, midinfrared pulses can be efficiently compressed in a dispersion-decreasing and nonlinearity-increasing tapered As₂S₃ PCF. Due to confinement loss in the tapered fiber, the efficiency of pulse compression is suppressed.

• Asian-Australasian Journal of Animal Sciences
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• 제18권6호
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• pp.780-786
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• 2005

This study presents a non-video, non-invasive, automatic, on-site monitoring system the system employs ultrasonic transducers to detect behavior in sows before, during and after parturition. An ultrasonic transmitting/receiving (T/R) circuit of 40 kHz was mounted above a conventional parturition bed. The T/R units use ultrasonic time-of-flight (TOF) ranging technology to measure the height of the confined sows at eight predetermined locations. From this data, three momentary postures of the sow are determined, characterized as standing-posture (SP), lateral-lying-posture (LLP) and sitting posture (STP). By examining the frequencies of position switch Stand-Up-Sequence (SUS) between standing-posture (SP), lateral-lying-posture (LLP) and sitting-posture (STP) rate can be determined for the duration of the sow' confinement. Three experimental pureblooded Landrace sows undergoing normal gestation were monitored for the duration of confinement. In agreement with common observation, the sows exhibited increased restlessness as parturition approached. Analysis of the data collected in our study showed a distinct peak in Stand-Up-Sequence (SUS, i.e. the transition from lying laterally to standing up ) and sitting-posture (STP) rate approximately 12 h prior to parturition, the observed peak being 5 to 10 times higher than observed on any other measurement day. It is concluded that the presented methodology is a robust, low-cost, lowlabor method for the continuous remote monitoring of sows and similar large animals for parturition and other behavior. It is suggested that the system could be applied to automatic prediction of sow parturition, with automatic notification of remote management personnel so human attendance at birth could reduce rates of sow and piglet mortality. The results of this study provide a good basis for enhancing automation and reducing costs in large-scale sow husbandry and have applications in the testing of various large mammals for the effects of medications, diets, genetic modifications and environmental factors.

• International Journal of Concrete Structures and Materials
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• 제4권2호
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• pp.89-96
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• 2010

This paper focuses on the effect of creep on the critical compressive strain (CCS) of concrete. The strain of concrete corresponding to the peak compressive stress is crucial in the selection of the ultimate yield strength of the reinforcing bar used in reinforced concrete columns. Among the various influencing factors, such as the creep, shrinkage, loading rate and confinement, the effect of creep and shrinkage is the most significant. So far, investigations into how these factors can affect the CCS of concrete have been rare. Therefore, to investigate the effect of creep and shrinkage on CCS, an experimental (part I) and a parametric study (part II) were conducted, as presented in these papers (part I considers creep effect, part II considers effect of creep and shrinkage). In part I, experiments pertaining to the loading age, loading rate, loading duration and loading and creep levels were conducted to study the effect of these variables on the CCS of concrete. It was found that the effects of the loading rate, loading age, and level and duration on the CCS of concrete were negligible. However, it is very important to consider the effect of creep.

• 통합자연과학논문집
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• 제8권3호
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• pp.147-152
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• 2015

Photoluminescent porous silicon (PSi) were prepared by an electrochemical etch of n-type silicon under the illumination with a 300 W tungsten filament bulb for the duration of etch. The red photoluminescence emitting at 620 nm with an excitation wavelength of 450 nm is due to the quantum confinement of silicon nanocrystal in porous silicon. As-prepared PSi was sonicated, fractured, and centrifuged in toluene to obtain photoluminescence silicon quantum dots. BET and BHJ methods were employed to study the specific surface area of as-prepared PSi. Optical characterization of red photoluminescent silicon nanocrystal was investigated by UV-vis and fluorescence spectrometer. Also SEM and TEM images of porous silicon and nanoparticles were investigated.

• Journal of Animal Science and Technology
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• 제55권4호
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• pp.325-330
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• 2013

Providing an adequate environment for horses is important to minimize the level of stress for domesticated horses. The objectives of this study were 1) to evaluate the effect of living conditions on stress level of horses, 2) to observe the effect of one month confinement on self-maintenance behavior and stereotypic behavior of horses. The experiment was conducted at National Institute of Animal Science, Equine Field Station (Seonghwan-eup, Korea). Horses were staying in the paddock prior to the experiment. On day 1, five horses were randomly selected and housed in metal fence panels stall. Six horses remained in the same paddock. The ratio of neutrophil to lymphocyte (on day 15) and cortisol (on day 1 and 29) from stalled horses were significantly higher than horses in the paddock. Duration or frequency of self-maintenance behaviors such as feeding, drinking, resting, walking was not significantly different between day 1 and day 29. However, the frequency of urination significantly decreased (p<0.05) on day 29 compared with day 1. The frequency of stereotypic behaviors was not different between day 1 and 29. Our data indicate that horses may be more stabled when they are staying in the paddock rather than staying in the stall, but the stress level of horses in the stall during one month confinement was not effective for horses to adapt stereotypic behavior. In conclusion, providing an adequate environment and stress-less horse management techniques can minimize the stress level of horses.

• 농촌의학ㆍ지역보건
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• 제29권2호
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• pp.303-314
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• 2004

본 연구대상의 작업특성을 조사한 결과 일년에 45회 정도 닭을 들여와 사육하였고, 양계업 종사년수는 최소 2년에서 최고 12년이었으며, 평균 종사 년수는 약 8년이었다. 닭을 사육하는 기간에는 일주일 내내 작업을 했고, 하루에 평균 6.3시간을 양계와 관련된 작업을 하며, 양계장 안에서 보내는 시간은 평균 3.3시간이었다. 14가지로 분류한 양계작업 중에서 닭의 입 출하와 분뇨처리는 외부인력과 함께 하거나, 외부인력에 맡기고 있었고, 이를 제외한 대부분의 일을 부부가 함께 하는 편이었다. 양계장의 사료 급여와 급수 시설은 자동시스템이었고, 환기창의 조절은 윈치커튼을 이용한 반자동 시스템이었다. 양계장의 환기는 겨울에는 강제환기를, 그 외 계절에는 자연환기 시스템을 사용하고 있었다. 계사의 바닥 재료는 왕겨를 사용하고 있었으며, 닭을 입하하기 전에 깔아서 출하한 다음에 제거하고 있었다. 양계장 내부애사 측정한 총 먼지와 호흡성 먼지의 지역시료 농도는 각각 평균 4.0mg/$m^3$(Range 3.16.8mg/$m^3$). 0.9mg/$m^3$(Range 0.41.8mg/$m^3$)였으며 호흡성 먼지의 개인노출량은 평균1.4mg/$m^3$(LOD미만 7.8mg/$m^3$)로 나타났다. 암모니아는 지역시료에서 평균 23.3ppm(Range 14.542.1ppm)이 측정되었고 개인노출량은 평균 22.2ppm(13.639.9ppm)으로 나타났다. 먼지의 지역시료 측정결과에서 총먼지에 대한 호흡성 먼지의 비율이 946%로 나타났고 호흡성 먼지 개인노출농도는 6개 농가 중 2개 농가의 개인노출량은 미국산업위생전문가협의회 (American Conference of Governmental Industrial Hygienist: ACGIH)의 노출기준치인3mg/$m^3$ 초과하였다(5.5mg/$m^3$, 7.8mg/$m^3$). 암모니아 개인노출농도 평균은 22.2ppm으로 ACGIH (시간가중)노출기준인 25ppm에 근접하였고, 34.2ppm, 39.9ppm 등 단시간노출기준(STEL) 35ppm과 비슷하거나 넘는 경우가 있어 매우 위험한 상황임을 알 수 있었다. 뿐만 아니라 양계장안에서 작업 중에 노출되는 먼지 또한 일반적인 호흡성먼지 보다 생물활성이 높은 유기먼지라는 점 등을 감안한다면 양계농업인의 건강영향은 매우 우려되는 바, 향후 의학적 검진이 병행되는 종합적인 조사가 필요할 것으로 판단된다.

• 대한간호학회지
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• 제8권1호
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• pp.139-151
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• 1978

This study is to observe the effects of nursing care according to change of position for comfort during labor and safe delivery of newborn infants and perturbment women. Fifty antepartal primipara with labor pain who were admitted to the delivery room of H University Medical Center from September 1, 1976 to November 15, 1976 (Estimate Delivery Confinement) were selected for this investigation. Among the 50 parturiencys, the experimental group (28 primipara) were placed in 30 degree upright sitting position and the control group (22 primipara) were placed in the supine position. following placement, both groups were observed. The summarized findings of the study were as follows; 1. There was a noticeably significant difference in the duration of the first stage of labor (defined as 4 cm. dilatation of the cervical os with the fetal presenting part engaged to full or 10 cm. dilatation) , between the two groups. For women in the 30 degree upright sitting position, the first stage of labor was close to 33.66 minutes shorter. than for the women in the supine position. (t : 32.79, D.F : 48, p<0.0,i) 2. Although slight differences were observed between the Apgar Scores of the newborn infants of primipara in the two groups, these were not significant. The mean Apgar Score among the newborn infants of primipara in the 30 degree upright sitting position was 9.64 compared with 9.04 for the newborn infants of primipara in the supine position, a difference of 0.6. (x$^2$= 2.44, D.F : 2, p〉0.05) 3. There was a significant difference in the conformability of the perturbment women between the two groups because the shortened duration of the first stage and the high level of comfort score calculated for six factors (body activity, serving bed pan, serving kidney basin, pushing, deep breathing and perturbment women's feelings), that affect nursing care.

• Journal of the Optical Society of Korea
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• 제20권1호
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• pp.135-139
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• 2016

I propose a vector passive harmonic mode-locked fiber laser based on topological insulator Bi2Se3 interacting with a fiber taper with a diameter of 7 μm. The particles of topological insulator are deposited uniformly onto the fiber taper with light pressure effect. By incorporating the fabricated saturable absorber into an Er-doped fiber laser cavity, stable mode-locked fiber is obtained. Due to the intense evanescent field of the fiber taper, strong confinement of light enhances the nonlinearity of the laser cavity, and passive harmonic mode-locking is performed. I observe a maximum harmonic mode-locking of 356th, corresponding to a frequency of 3.57 GHz. The pulse duration is 824 fs, and the full width at half maximum of the spectrum is about 8.2 nm. The polarization dependent loss of the saturable absorber is ~ 2.5 dB in the wavelength range of the C band. As the cavity contains no other polarization dependent device, the mode-locked laser is functioning in the vector state. The harmonic order vs pump power is investigated. To the best of our knowledge, this report is the highest frequency mode-locked fiber laser based on Bi2Se3. Experimental results indicate that the topological insulator Bi2Se3 functioning with a thin fiber taper is effective for vector harmonic mode-locking.