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Experimental Performance Evaluation of Steel Mesh as Maintenance and Reinforcement Materials (Steel Mesh Cement Mortar의 보수⋅보강 성능 평가)

  • Kim, Yeon-Sang;Choi, Seung-Jai;Kim, Jang-Ho Jay
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.4
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    • pp.50-58
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    • 2014
  • Due to the cost burden of new construction, the necessity of repair and retrofitting of aged structures is sharply increasing as the domain of repair and retrofitting construction is expanding. Because of the necessity, new technologies for repair and retrofitting are continuously studied in Korea and foreign countries. Steel adhesive method, fiber reinforced plastic (FRP) surface adhesive method, and external prestressing method are used to perform the repair and retrofitting works in Korea. In order to consider a repair method using steel mesh reinforced cement mortar (SMCM), 3-point flexural member test was conducted considering repair area and layer number of SMCM. Five types of specimens including ordinary reinforced concrete (RC) specimen with dimensions of $1400{\times}500{\times}200$ (mm) were cast for testing the deflection measurement, a LVDT was installed at the top center of the specimens. Also, a steel strain gauge and a concrete strain gauge were placed at the center of the specimens. A steel strain gauge was also installed on the shear reinforcement. The 3 point flexural member test results showed that the maximum load of SMCM reinforced specimen was higher than that of basic RC specimen in all of the load-displacement curves. Also, the results showed that, when the whole lower part of the basic RC specimen was reinforced, the maximum load and strain were 1.18 and 1.37 times higher than that of the basic RC specimen, respectively. Each specimen showed a slightly different failure behavior where the difference of the results was caused by the difference in the adhesive level between SMCM and RC. Particularly, in SM-B1 specimen, SMCM spalled off during the experiment. This failure behavior showed that the adhesive performance for RC must be improved in order to utilize SMCM as repair and retrofitting material.

Evaluation of clinical status of removable partial dentures (가철성 국소의치의 임상적 상태에 대한 평가)

  • Yang, Dong-Seok;Cho, Uk;Jeong, Chang-Mo;Jeon, Young-Chan;Yun, Mi-Jung
    • The Journal of Korean Academy of Prosthodontics
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    • v.47 no.3
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    • pp.320-327
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    • 2009
  • Statement of Problem: Although many efforts have been continually made to estimate long term prognosis of removable partial dentures, the complication of removable partial dentures was still found because of inaccurate fabrication procedure and improper maintenance care. Purpose: The purpose of this study was to evaluate the clinical status of removable partial dentures. Material and methods: A total of 112 individuals with 153 removable partial dentures (35 - 87 years, 64 women and 48 men) were examined by intra-oral examination, diagnostic cast and radiographic examination. Results and conclusion: The results of this study were as follows: 1. Length of service of removable partial dentures was $5.3{\pm}4.3$ years (mean), 4.0 years (median). 2. A total of 45 removable partial dentures were considered failures. The loss of 18 abutments of 369 was founded. 3. Type of arch, Kennedy classification and type of opposite dentition were found to have no influence on longevity and success rate of removable partial dentures (P > .05). 4. Most common major connector was the palatal plate in maxilla and the number of lingual bar and linguoplate designed in mandible were similar. 5. The circumferential type retainer was the most commonly used retainer. 6. Sixty-three percent of the class I and II removable partial dentures incorporated indirect retention into the design. 7. Approximately 81% of the removable partial dentures had at least one defect. Excessive wear of posterior teeth (27.9%), lack of integrity (23.2%), lack of stability (22.6%) were frequent defects of removable partial dentures.

Shear bond strength of Universal bonding systems to Ni-Cr alloy (니켈-크롬 합금에 대한 다용도 접착 시스템의 전단결합강도)

  • Song, So-Yeon;Son, Byung-Wha;Kim, Jong-Yeob;Shin, Sang-Wan;Lee, Jeong-Yol
    • The Journal of Korean Academy of Prosthodontics
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    • v.53 no.4
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    • pp.295-300
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    • 2015
  • Purpose: The aim of this study was to evaluate the shear bond strength between Ni-Cr alloy and composite resin using universal adhesive systems coMPared to conventional method using metal primers. Materials and methods: For this study, a total of 120 cast commercial Ni-Cr alloy (Vera Bond 2V) disks were embedded in acrylic resin, and their surfaces were smoothed with silicon carbide papers and airborne-particle abrasion. Specimens of each metal were divided into 6 groups based on the combination of metal primers (Metal primer II, Alloy primer, Metal & Zirconia primer, MKZ primer) and universal adhesive systems (Single Bond Universal, All Bond Universal). All specimens were stored in distilled water at $37^{\circ}C$ for 24 hours. Shear bond strength testing was performed with a universal testing machine at a cross head speed of 1 m/min. Data (MPa) were analyzed using one-way ANOVA and the post hoc Tukey's multiple comparison test (${\alpha}$=.05). Results: There were significant differences between Single Bond Universal, All Bond Universal, Metal Primer II and Alloy Primer, MKZ Primer, Metal & Zirconia Primer (P<.001). Conclusion: Universal Adhesive system groups indicated high shear bond strength value bonded to Ni-Cr alloy than that of conventional system groups using primers except Metal Primer II. Within the limitations of this study, improvement of universal adhesive systems which can be applied to all types of restorations is recommended especially non-precious metal alloy. More research is needed to evaluate the effect of silane inclusion or exclusion in universal adhesive systems.

Acute Kidney Injury Models: Focus on the Therapeutic Effects of Stem Cell in Preclinical Approach (줄기세포 연구를 위한 급성신장손상 모델)

  • Nam, Hyun-Suk;Woo, Jae-Seok;Woo, Heung-Myong
    • Journal of Veterinary Clinics
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    • v.27 no.5
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    • pp.533-539
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    • 2010
  • Stem cell-based therapy is under intensive investigation to treat acute renal failure (ARF). The purpose of this study was to evaluate available ARF models, and suggest a model appropriate to therapeutic evaluation of the stem cells in preclinical approach by determining the optimum concentration of nephrotoxic agents and duration of ischemia induction. Three different types of available acute kidney injury (AKI) animal models were analyzed using rats: Cisplatin (saline, 5 and 7.5 mg/kg, IP) or glycerol (saline, 8 and 10 ml/kg, IM)-induced nephrotoxicity as toxic models and ischemia-induced (sham, 35 and 45 minutes) nephropathy as an ischemic model. The relevance and applicability to investigate especially the regenerative ability of stem cells were evaluated regarding morphology, renal function and survival at this time point. In the point of renal function, 10 ml glycerol/kg and 7.5 mg cisplatin/kg model in toxic models and 45 min model in ischemia models showed significant decrease for the longer observation time compared to 8 ml glycerol/kg, 5 mg cisplatin/kg and the 35 min ischemia models, respectively. All groups were observed no mortality except 45 min-ischemia model with 50% survival. Histological significant alterations including cast formation in the tubular lumen, tubular necrosis and apoptosis were revealed on the second day in either ischemiaor glycerol-induced models, and on day 5 in cisplatin-induced models. The results indicate that ischemia 35 min-, cisplatin 7.5 mg/kg- and glycerol 10 ml/kg-induced AKI would be ideal animal models to monitor a outcome parameter related to the therapeutic effects on renal function with noninvasive techniques in the same animal at multiple time points. Our findings also suggest that the best time points for the functional or histological interpretation of renal will be on day 2 in both glycerol- and ischemia-induced AKI models and on day 5 in cisplatin-induced AKI.

Characteristics of Corrosion and Water Quality in Simulated Reclaimed Water Distribution Pipelines (모형 재이용관을 이용한 하수재이용수의 부식 및 수질영향 연구)

  • Kang, Sung-Won;Lee, Jai-Young;Lee, Hyun-Dong;Kim, Gi-Eun;Kwak, Pill-Jae
    • Journal of Korean Society of Environmental Engineers
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    • v.34 no.7
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    • pp.473-479
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    • 2012
  • Water reuse has been highlighted as a representative alternative to solve the lacking water resource. This study carried out a study on the pipe corrosion and water quality change which can occur through the supply of reclaimed water, using a simulated reclaimed water distribution pipeline. Galvanized steel pipe (GSP), cast iron pipe (CIP), stainless steel pipe (STSP) and PVC pipe (PVCP) were used for the pipe materials. Reclaimed water(RW) and tap water(TW) were respectively supplied into simulated reclaimed water distribution pipelines. As a result of performing a loop test to supply reclaimed water to simulated reclaimed water distribution pipelines, the weight reduction of pipe coupons showed the sequence of CIP > GSP > STSP ${\approx}$ PVCP. In addition, reclaimed water showed a high corrosion rate comparing to that of tap water. In case of CIP, the initial corrosion rate showed 3.511 mdd(milligrams per square decimeter per day) for reclaimed water and 2.064 mdd for tap water and the corrosion rate for 90 days showed 0.833 mdd for reclaimed water and 0.294 mdd for tap water. Also in case of GSP, the initial corrosion rate showed 2.703 mdd for reclaimed water and 2.499 mdd for tap water and the corrosion rate for 90 days showed 0.349 mdd for reclaimed water and 0.248 mdd for tap water, which was a tendency similar to that appeared in CIP with a tendency to reduce the corrosion rate. As a result of water quality changes of reclaimed water at pipe materials to carry out the loop test, there was higher conversion ratio of ammonia into nitrate in CIP and GSP with higher corrosion rate than that in STSP and PVCP where no corrosion has occurred. The highest denitrification rate of nitrate could be observed from CIP with the most particles generated from corrosion. In CIP, it could be confirmed that there was MIC (Microbiologically Induced Corrosion) as a result of EDS (Energy Dispersive X-ray spectrometer System) analysis results.

Fish Community Characteristics and Habitat Aspects of Endangered Species Pseudopungtungia tenuicorpa and Acheilognathus signifer in the Hwayangcheon Stream, Hangang River of Songnisan National Park, Korea (속리산국립공원 화양천의 어류군집 특성 및 멸종위기종 가는돌고기 Pseudopungtungia tenuicorpa와 묵납자루 Acheilognathus signifer의 서식양상)

  • Ko, Myeong-Hun;Han, Mee-Sook;Myung, Ra-Yeon;Yun, Hyeong-Jin
    • Korean Journal of Ichthyology
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    • v.31 no.4
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    • pp.222-234
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    • 2019
  • Fish community characteristics and habitat aspects of endangered species, Pseudopungtungia tenuicorpa and Acheilognathus signifer were investigated in the Hwayangcheon Stream of Songnisan National Park, a tributary of the Hangang River, Korea from April to October 2018. During this period, there were 29 species of 8 families collected from 11 survey stations using kick nets, cast nets long bag set nets. The dominant and subdominant species were Zacco koreanus (38.81%) and Rhynchocypris oxycephalus (16.64%), respectively. The next most abundant species were Z. platypus (14.28%), Pungtungia herzi (6.92%), Hemibarbus longirostris (4.52%), Pseudogobio esocinus (3.51%), A. signifer (2.31%) and P. tenuicorpa (1.90%). Among the fish collected, 18 species (62.1%) were Korean endemic species. Endangered species were A. signifer, P. tenuicorpa and Gobiobotia brevibarba. From upstream to downstream, the dominance index has gradually decreased, but number of species and individuals, diversity and evenness has gradually increased. Also, river health (index of biological integrity) is assessed as good (St. 1~8) and very good (St. 9~11). Fish communities were divided into four sections by the similarity index based on species and their numbers, i.e., upper section (St. 1~2, 4~5), upper-middle section (St. 3, 6), middle section (St. 7~9) and lower section (St. 10~11). Endangered species, Pseudopungtungia tenuicorpa inhabited in mostly lower section (St. 10~11) with rock and boulder bottoms, and age groups in April estimated from total length indicated that the 44~61 mm group is 1 year old, the 66~81 mm group is 2 years old, the 88~99 mm group is 3 years old, and the 104~107 mm group is more than 4 years old. Also, endangered species, A. signifer inhabited in middle-lower section (St. 7~11) with boulder and cobble bottoms and slow velocity, which the place inhabited by water plants. Meanwhile, their age structure in April estimated from total length indicated that the 30~43 mm group is 1 year old, the 48~58 mm group is 2 years old, the 62~77 mm group is 3 years old, and the 84~100 mm group is more than 4 years old. The sex ratio of female (47) to male (42) was 1 : 0.89.

A LIGHT AND ELECTRON MICROSCOPIC STUDY OF CHANCES IN INTERMAXILLARY SUTURE DURING THE RAPID MAXILLARY EXPANSION OF YOUNG ADULT DOGS (유성견 급속정중이개시 정중구개봉합부위의 조직학적 변화에 대한 연구)

  • Lee, Doo-Hee;Chung, Kyu-Rhim
    • The korean journal of orthodontics
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    • v.26 no.2 s.55
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    • pp.153-162
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    • 1996
  • Rapid maxillary expansion is widely used for the correction of anteroposterior discrepancies, constriction of the maxillary arch, etc. This experiment was undertaken to examine the serial changes in the osteogenesis as well as the collagen fiber bundles in the intermaxillary suture during the rapid maxillary expansion treatment. Four young female dogs aged 6 to 8 months old and not showing menarche yet were used for the experiment. The maxillary impression of dogs were taken, expansion device cast and Hyrax screw soldered at the midline in the 1st premolar area. RME device was delivered to the dogs and the activation of 0.25 mm per quarter-turn was done 2 times per day for 10 days until 5 mm separation was made. Separation of the maxilla was confirmed by X-ray. The animals were sacrificed on 0, 15, 30, 60 days from the finish of maxillary separation and preparations for light microscopy and surface electron microscopy were made. The sutures were cut into frontal serial sections for examination of the histological reactions. The following results were obtained and the conclusions made. 1. The edges of the two palatal plates bordering the midpalatal suture which at the beginning of the retention period were mainly composed of compact bone, underwent extensive resorption followed by new bone formation and gradually became spongy bone rich in bone marrow which in the 60 day retention animal became the compact bone with short intermaxillary suture space. During this transformation, newly formed trabecular bone tissues were added to the original margin. 2. Throughout the expansion period, the collagen fibers underwent successive changes such as stretching, loss of polarity, and finally fibrillogenesis. Towards the end of the expansion procedure, sharpey's fiber formation in newly formed bones were observed. 3. Bony spicules were found in the initial stage of retention on occlusal topographic X-rays, which later were confirmed to have ossified. 4. Judging from the histological changes occuring during the experimental expansion, excessive expansion will cause an excessive bleeding, and retard the remodeling of intermaxillary suture. According to the above results, the bone remodeling after rapid maxillary expansion was preceded by the migration of migratory cells into the intermaxillary suture area. The bone remodeling phenomena were on-going during the 2 months retention sample.

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Dietitians′ Perception on Usage of Cook/chill Vegetables in Institution Foodservice (단체급식 소에서의 냉장조리 채소의 이용에 대한 영양사의 인식조사)

  • 류은순;이동선
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.30 no.6
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    • pp.1293-1300
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    • 2001
  • We surveyed dietitians'perception on usage of cook/chill vegetables, The questionnaires were distributed to 245 dietitians working in elementary schools and other institutions in Busan area. According to the survey, 75.9% of the dietitians perceived that minimally processed ready -to-use vegetal)toes would be helpful for the institutional foodservice They answered that problems of vegetable usage in the foodservice mainly come from long preparation time (45.4%), a large quantity of leftover (13.1%), and a high ratio of disuse (16.0%). Degree of preparedness from raw vegetables was highest for garlic, and was in tile order of platicodcm, onions, carrots, Potatoes, Korean cabbage and radish.40.9% of the dietitians answered that it was necessary Ic develop cook/chill vegetables in their institute restaurants. The high career group ( >6 yrs.) was, however, significantly (p<0.05) negative against the use of cooHchill vegetables. The dietitians were expecting that developing cook/chill vegetables would save cooking time and processes (4.43/5.00), and reduce waste (4.53/5.00) greatly. They also estimated that focal hygiene and quality would be improved, and labor cast be reduced moderately. On the other hand, they thought that the cost of flood would not be reduced.

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The Tooth Size RelaTionship Between Crowding Patients and Normal Subjects in Korean (총생치열을 갖는 교정환자와 정상인의 치아크기 비교)

  • Han, Man-Deuk;Jeon, Eun-Sook
    • Journal of dental hygiene science
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    • v.6 no.1
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    • pp.29-34
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    • 2006
  • This study was undertaken to compare the tooth and arch size between crowding patient and normal subjects. Two group of dental casts were selected on the basis of crowding patients and normal subjects. One group, consisting of 40 pair of dental casts(20 male and 20 female), exhibited noncrowded dentitions. A second group, consisting of 40 pairs of dental cast(21 male and 21 female), exhibited remarkably crowding need for orthodontic treatment. Tooth width measurements were made with a sliding digital caliper with Vernier scale neared 0.01 mm. Mean, standard deviation, T-test of the following parameters were used to compare two group : individual mesiodistal crown widths, arch width and arch length. The following result were obtained. In the mesiodistal crown widths, normal subjects had generalized larger teeth than Wheeler's results(human tooth size index), except for maxillary central incisor, maxillary 2nd premolar, mandibular canine, and mandibular 1st molar. In the orthodontic patients with crowded dentitions, the mesiodistal tooth crown widths were generalized larger teeth than noncrowded normal subjects. In the arch width and arch length, the crowded dentition group had smaller arch width and arch length than the normal group.

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Recent Progress in Air-Conditioning and Refrigeration Research : A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2013 (설비공학 분야의 최근 연구 동향 : 2013년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.12
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    • pp.605-619
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    • 2014
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2013. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of fluid machinery, pipes and relative parts including orifices, dampers and ducts, fuel cells and power plants, cooling and air-conditioning, heat and mass transfer, two phase flow, and the flow around buildings and structures. Research issues dealing with home appliances, flows around buildings, nuclear power plant, and manufacturing processes are newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for general analytical model for desiccant wheels, the effects of water absorption on the thermal conductivity of insulation materials, thermal properties of Octadecane/xGnP shape-stabilized phase change materials and $CO_2$ and $CO_2$-Hydrate mixture, effect of ground source heat pump system, the heat flux meter location for the performance test of a refrigerator vacuum insulation panel, a parallel flow evaporator for a heat pump dryer, the condensation risk assessment of vacuum multi-layer glass and triple glass, optimization of a forced convection type PCM refrigeration module, surface temperature sensor using fluorescent nanoporous thin film. In the area of pool boiling and condensing heat transfer, researches on ammonia inside horizontal smooth small tube, R1234yf on various enhanced surfaces, HFC32/HFC152a on a plain surface, spray cooling up to critical heat flux on a low-fin enhanced surface were actively carried out. In the area of industrial heat exchangers, researches on a fin tube type adsorber, the mass-transfer kinetics of a fin-tube-type adsorption bed, fin-and-tube heat exchangers having sine wave fins and oval tubes, louvered fin heat exchanger were performed. (3) In the field of refrigeration, studies are categorized into three groups namely refrigeration cycle, refrigerant and modeling and control. In the category of refrigeration cycle, studies were focused on the enhancement or optimization of experimental or commercial systems including a R410a VRF(Various Refrigerant Flow) heat pump, a R134a 2-stage screw heat pump and a R134a double-heat source automotive air-conditioner system. In the category of refrigerant, studies were carried out for the application of alternative refrigerants or refrigeration technologies including $CO_2$ water heaters, a R1234yf automotive air-conditioner, a R436b water cooler and a thermoelectric refrigerator. In the category of modeling and control, theoretical and experimental studies were carried out to predict the performance of various thermal and control systems including the long-term energy analysis of a geo-thermal heat pump system coupled to cast-in-place energy piles, the dynamic simulation of a water heater-coupled hybrid heat pump and the numerical simulation of an integral optimum regulating controller for a system heat pump. (4) In building mechanical system research fields, twenty one studies were conducted to achieve effective design of the mechanical systems, and also to maximize the energy efficiency of buildings. The topics of the studies included heating and cooling, HVAC system, ventilation, and renewable energies in the buildings. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment is mostly focused on indoor environment and building energy. The main researches of indoor environment are related to infiltration, ventilation, leak flow and airtightness performance in residential building. The subjects of building energy are worked on energy saving, operation method and optimum operation of building energy systems. The remained studies are related to the special facility such as cleanroom, internet data center and biosafety laboratory. water supply and drain system, defining standard input variables of BIM (Building Information Modeling) for facility management system, estimating capability and providing operation guidelines of subway station as shelter for refuge and evaluation of pollutant emissions from furniture-like products.