Effect of Impact Load on Splice Length of Reinforcing Bars

Hyeon?Jong Hwang,Fan Yang,Li Zang,Jang?Woon Baek,Gao Ma 한국콘크리트학회 2020 International Journal of Concrete Structures and M Vol.14 No.5

Impact loading damage of reinforced concrete (RC) members deteriorates bond strength of reinforcing bars. To understand the effect of strain rate on the bond strength of reinforcing bars in RC beams under impact load, drop hammer test was performed on twenty-four simply supported RC beams with lap spliced bars at the mid-span. The test parameters were reinforcing bar diameter, splice length, drop height, and hammer mass. The dynamic responses including the impact load history, mid-span deflection history, crack distribution, and strain history of reinforcing bar were evaluated. Although the designed bar development length was 31–69% of the requirement of current design codes under static load, the tensile strength of bar splices was greater than the dynamic yield strength when subjected to large impact energy under impact load. On the basis of the test results, existing design equations for the bar development length under static load were modified to consider the impact loading effect on the bond strength. Factors related to the strain rate effect of materials, impact damage, and impact energy loss were proposed. The prediction of the proposed method agreed well with the tensile strength of bar splices under impact load.

골격성 Ⅲ급 부정교합자에서 중심위 변위가 두부 방사선 계측치에 미치는 영향

박양수,김종철,황현식 대한치과교정학회 1996 대한치과교정학회지 Vol.26 No.3

본 연구는 Ⅲ급 부정교합자에서 중심교합상태의 두부 방사선 사진과 MPI 수치를 이용하여 중심위로 전환한 두부 방사선 사진(Centrically related cephalometrics)를 계측하여 중심위 변위시 유의한 계측치 변화가 있는지 확인하고자 시행되었다. 교정치료의 경험이 없는 25명의 Ⅲ급 부정교합군과 25명의 정상교합군을 대상으로 하여, 중심교합위 상태의 측모 두부 방사선 사진과 중심위 및 중심교합위 기록을 채득하고, 모형을 SAMⅡ 교합기에 부착하였다. 중심위 변위량은 MPI(Mandibular Position Indicator)를 이용하여 계측하였으며, MPI 수치와 중심교합위 상태의 측모 두부 방사선 사진의 투사도를 이용하여 Conversion work sheet상에서 중심위 전환을 시행하였다. 두부 상사선 계측 항목은 하악골의 위치와 관계되는 것을 선택하였다. 정상교합군과 Ⅲ급 부정교합군에서 중심위와 중심교합위간의 계측치 변화를 연구하여 다음과 같은 결과를 얻었다. 1. 하악 과두에서의 중심위 변위량은 정상교합군에서 전후방 변위량(ΔX)0.56±0.50mm, 수직적 변위량(ΔZ) -0.61±0.53mm였으며, Ⅲ급 부정교합군에서 전후방 변위량 (ΔX) 0.093±0.77mm, 수직적 변위량(ΔZ) -0.64±0.89mm로, 두군 보두 후하방 변위양상을 나타냈다. Ⅲ급 부정교합군에서 정상교합군보다 전후방 변위량이 더 크게 나타났으나 통계학적인 유의성은 없었다. 2. 중심교합위와 중심위 두부 방사선 사진의 계측치를 비교해 본 결과 정상 교합군에서 ANB, Facial angle, Facial convexity, ODI 등의 항목이 유의한 차이를 나타냈다. Ⅲ급 부정 교합군에서는 ANB, Facial angle, facial convexity, ODI, SNB, APDI, L1-FP 등 유의한 차이를 보이는 항목이 더 많았고 유의성도 더 높게 나타났다. 3. 두부 방사선 사진의 계측치 변화는 중심위 변위와는 연관성이 있었으나, 정상교합군과 Ⅲ급 부정교합군에 대한 연관성이 없었다. 이상의 결과는 중심의 변위량이 임상적으로 재현할 수 있는 중심위 위치에서 정상적으로 변위되는 양보다 큰 경우 중심위는 교정 환자에서 적절한 진단과 치료 계획 수립을 위한 기준 점으로 고려되어야 함을 시사하였다. The purpose of this study was to investigate if there were a significant difference between cephalometric measurements of mandibular position derived from a centric occlusion tracing compared to those of a converted centric relation tracing in the Class Ⅲ malocclusion. The sample consisted of 25 ClassⅢ malocclusion and 25 normal occlusion persons who had no orthodontic treatment. The records included an lateral cephalometrics in centric occlusion, centric relation and centric occlusion bite registration and diagnostic casts mounted on the SAM Ⅱ articulator in CR. The amount of CR-CO discrepancy of condyle was recorded using a MPI(Mandibular Position Indicator, MPI 200, Great Lakes Orthodontics, USA). The conversion of the CO cephalogram to CR using the MPI readings was performed on the Conversion work sheet. Measures of mandibular position were chosen for the purpose of this study. The comparison of the difference between CO and CR cephalometric measurements in the normal occlusion and Class Ⅲ malocclusion group were studied. The results were as follows: 1. In the features of CR-CO discrepancy of the condyle, the condyle was displaced posterior and inferior when the teeth were in centric occlusion. The horizontal component(ΔX) in Class Ⅲ malocclusion group was greater than the vertical component(ΔX) and also greater than the horizontal component(ΔZ) in normal occlusion group. There was no statistically significant correlation between MPI measurements and the groups of normal occlusion and Class Ⅲ malocclusion group. 2. In the comparison of the cephalometric measurements in each group, Normal occlusion group showed significant difference in measurements such as ANB, Facial angle, Facial convexity and ODI. ClassⅢ malocclusion group showed significant difference in measurements such as ANB, Facial angle, Facial convexity, OEI, SNB, APDI, L1-FP and it had more significance than the normal occlusion group. 3. The Value of cephalometric measurements was significantly different between CO and CR but there were no differences between the groups of normal occlusion and Class Ⅲ malocclusion. The results of this study suggest that if the discrepancies are greater than the amount of normal displacement from clinically captured centric relation, centric relation should be considered as the starting point for proper diagnosis and treatment planning.

마이크로 밀링시스템에서 레버구조의 피에조구동기 설계

고태조,정병묵,양현모,박종권 한국공작기계학회 2008 한국공작기계학회 추계학술대회논문집 Vol.2008 No.-

High precision machining technology has become one of the important parts in the development of a precision machine. Such a machine requires high speed on a large workspace as well as high precision positioning. For machining systems having a long stroke with ultra precision, a micro stage system with lever mechanism is proposed in this paper. The proposed micro stages are activated by the piezo-actuators with high precision, however, they have severe disadvantage for the travel range that the stroke is limited to a few microns. Because it is not easy to increase the stroke of piezo-actuator, it is very difficult to make an X-Y stage with only piezo-actuators. Therefore, in order to increase it, this paper proposes a lever mechanism for the piezo-actuator stage. In the experiments, we can confirm that the stroke is increased more than three times and it is possible to implement the micro X-Y stage using piezo-actuators.

Rifampicin에 의한 것으로 추정되는 위막성 대장염1예

김수현,이은우,정종혁,문승현,김동한,양혁승,오영상,김호동,김도현,박혁,박정환,박경옥,이영직 朝鮮大學校 附設 醫學硏究所 2006 The Medical Journal of Chosun University Vol.31 No.2

Pseudomembranous colitis, caused by altering the normal colonic flora and allowing the multiplication of Clostridium difficile, is an deleterious adverse effect of antibiotics. But it is rarely reported by rifampicin. Rifampicin is one of the first line drug in the treatment of tuberculosis and many patients are exposed to its potential adverse effects. We experienced a patient that had abdominal discomfort and hematochezia due to pseudomembranous colitis after receiving antituberculous medication, and which was probably caused by rifampicin. A 82 years old man was admitted with abdominal discomfort and hematochezia for one week. On the past history he had been diagnosed as endobronchial tuberculosis about 4 months ago. Colonoscopy revealed multiple discrete whitish mucosal lesion on rectosigmoid colon, and histologic findings were consistent with pseudomembranous colitis. The antituberculous agents were discontinued and vancomycin was administered. The patient's symptoms were resolved within several days. There was no recurrence after reinstitution of the antituberculous agents excluding rifampicin. We report here on a case of pseudomembranous colitis probably due to rifampicin.

Impact of perinatal environmental tobacco smoke on the development of childhood allergic diseases

Hyeon-Jong Yang 대한소아청소년과학회 2016 Clinical and Experimental Pediatrics (CEP) Vol.59 No.8

Allergic diseases such as asthma, allergic rhinitis, atopic dermatitis, and food allergy, are most common chronic, noncommunicable diseases in childhood. In the past few decades, the prevalence has increased abruptly worldwide. There are 2 possible explanations for the rising prevalence of allergic diseases worldwide, that an increased disease-awareness of physician, patient, or caregivers, and an abrupt exposure to unknown hazards. Unfortunately, the underlying mechanisms remain largely unknown. Despite the continuing efforts worldwide, the etiologies and rising prevalence remain unclear. Thus, it is important to identify and control risk factors in the susceptible individual for the best prevention and management. Genetic susceptibility or environments may be a potential background for the development of allergic disease, however they alone cannot explain the rising prevalence worldwide. There is growing evidence that epigenetic change depends on the gene, environment, and their interactions, may induce a long-lasting altered gene expression and the consequent development of allergic diseases. In epigenetic mechanisms, environmental tobacco smoke (ETS) exposure during critical period (i.e., during pregnancy and early life) are considered as a potential cause of the development of childhood allergic diseases. However, the causal relationship is still unclear. This review aimed to highlight the impact of ETS exposure during the perinatal period on the development of childhood allergic diseases and to propose a future research direction.

Mechanism of resistance acquisition and treatment of macrolide-resistant Mycoplasma pneumoniae pneumonia in children

Yang, Hyeon-Jong,Song, Dae Jin,Shim, Jung Yeon The Korean Pediatric Society 2017 Clinical and Experimental Pediatrics (CEP) Vol.60 No.6

Mycoplasma pneumoniae pneumonia (MPP) is one of the most common forms of community-acquired pneumonia in children and adolescents. Outbreaks of MPP occur in 3- to 7-year cycles worldwide; recent epidemics in Korea occurred in 2006-2007, 2011, and 2015-2016. Although MPP is known to be a mild, self-limiting disease with a good response to macrolides, it can also progress into a severe and fulminant disease. Notably, since 2000, the prevalence of macrolide-resistant MPP has rapidly increased, especially in Asian countries, recently reaching up to 80%-90%. Macrolide-resistant Mycoplasma pneumoniae (MRMP) harbors a point mutation in domain V of 23S rRNA with substitutions mainly detected at positions 2063 and 2064 of the sequence. The excessive use of macrolides may contribute to these mutations. MRMP can lead to clinically refractory pneumonia, showing no clinical or radiological response to macrolides, and can progress to severe and complicated pneumonia. Refractory MPP is characterized by an excessive immune response against the pathogen as well as direct injury caused by an increasing bacterial load. A change of antibiotics is recommended to reduce the bacterial load. Tetracyclines or quinolones can be alternatives for treating MRMP. Otherwise, corticosteroid or intravenous immunoglobulin can be added to the treatment regimen as immunomodulators to downregulate an excessive host immune reaction and alleviate immune-mediated pulmonary injury. However, the exact starting time point, dose, or duration of immunomodulators has not been established. This review focuses on the mechanism of resistance acquisition and treatment options for MRMP pneumonia.

Development of a PCR marker for monitoring of transgene introgression in resveratrol-enriched transgenic rice plant

Yang Qin,So-Hyeon Baek,Soon-Jong Kweon,Taek-Ryoun Kwon,Myung-Ho Lim,Kong-Sik Shin,Hyun-Suk Cho,Hee-Jong Woo 한국육종학회 2015 한국육종학회 심포지엄 Vol.2015 No.07

A variety of genetically modified (GM) crops have been developed in Korea. In these crops, the resveratrol-enriched transgenic rice plant has moved ahead to generate the dossier for regulatory review process required for commercialization of GM crop. The resveratrol-enriched transgenic rice plant could be released to farmers for cultivation after national regulators have determined that it is safe for the environment and human health. Here we developed a PCR-based DNA marker based on flanking sequences of transgene for the discrimination of zygosity in resveratrol-enriched transgenic rice plant. This DNA marker will be useful for identifying of resveratrol-enriched transgenic rice plant, and can also be use to estimate transgene movement occurred by pollen transfer or seed distribution.

Critical rate of electrolyte circulation for preventing zinc dendrite formation in a zinc–bromine redox flow battery

Yang, Hyeon Sun,Park, Jong Ho,Ra, Ho Won,Jin, Chang-Soo,Yang, Jung Hoon Elsevier 2016 Journal of Power Sources Vol.325 No.-

<P><B>Abstract</B></P> <P>In a zinc–bromine redox flow battery, a nonaqueous and dense polybromide phase formed because of bromide oxidation in the positive electrolyte during charging. This formation led to complicated two-phase flow on the electrode surface. The polybromide and aqueous phases led to different kinetics of the Br/Br<SUP>−</SUP> redox reaction; poor mixing of the two phases caused uneven redox kinetics on the electrode surface. As the Br/Br<SUP>−</SUP> redox reaction was coupled with the zinc deposition reaction, the uneven redox reaction on the positive electrode was accompanied by nonuniform zinc deposition and zinc dendrite formation, which degraded battery stability. A single-flow cell was operated at varying electrolyte circulation rates and current densities. Zinc dendrite formation was observed after cell disassembly following charge–discharge testing. In addition, the flow behavior in the positive compartment was observed by using a transparent version of the cell. At low rate of electrolyte circulation, the polybromide phase clearly separated from the aqueous phase and accumulated at the bottom of the flow frame. In the corresponding area on the negative electrode, a large amount of zinc dendrites was observed after charge–discharge testing. Therefore, a minimum circulation rate should be considered to avoid poor mixing of the positive electrolyte.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Polybromide and aqueous phases led to different kinetics of Br/Br<SUP>−</SUP> redox reaction. </LI> <LI> Poor mixing of the two phases caused uneven redox kinetics on positive electrode. </LI> <LI> Uneven reaction on positive electrode was accompanied by zinc dendrite formation. </LI> <LI> Zinc dendrite formation degraded battery stability. </LI> <LI> Therefore, a minimum circulation rate should be set to avoid poor mixing. </LI> </UL> </P>

Prenatal particulate matter affects new asthma via airway hyperresponsiveness in schoolchildren

Yang, Song‐,I,Lee, So‐,Yeon,Kim, Hyo‐,Bin,Kim, Hwan‐,Cheol,Leem, Jong‐,Han,Yang, Hyeon‐,Jong,Kwon, Hyeok,Seo, Ju‐,Hee,Cho, Hyun‐,Ju,Yoon, Jisun,Lee, Eun Wiley (Blackwell Publishing) 2019 Allergy Vol.74 No.4

Impact of perinatal environmental tobacco smoke on the development of childhood allergic diseases

Yang, Hyeon-Jong The Korean Pediatric Society 2016 Clinical and Experimental Pediatrics (CEP) Vol.59 No.8

Allergic diseases such as asthma, allergic rhinitis, atopic dermatitis, and food allergy, are most common chronic, noncommunicable diseases in childhood. In the past few decades, the prevalence has increased abruptly worldwide. There are 2 possible explanations for the rising prevalence of allergic diseases worldwide, that an increased disease-awareness of physician, patient, or caregivers, and an abrupt exposure to unknown hazards. Unfortunately, the underlying mechanisms remain largely unknown. Despite the continuing efforts worldwide, the etiologies and rising prevalence remain unclear. Thus, it is important to identify and control risk factors in the susceptible individual for the best prevention and management. Genetic susceptibility or environments may be a potential background for the development of allergic disease, however they alone cannot explain the rising prevalence worldwide. There is growing evidence that epigenetic change depends on the gene, environment, and their interactions, may induce a long-lasting altered gene expression and the consequent development of allergic diseases. In epigenetic mechanisms, environmental tobacco smoke (ETS) exposure during critical period (i.e., during pregnancy and early life) are considered as a potential cause of the development of childhood allergic diseases. However, the causal relationship is still unclear. This review aimed to highlight the impact of ETS exposure during the perinatal period on the development of childhood allergic diseases and to propose a future research direction.