• Hip & pelvis
• /
• v.30 no.4
• /
• pp.269-275
• /
• 2018

Purpose: The purpose of this study is to describe a method of inserting cement in the femoral head before fixation with dynamic hip screw to prevent screw cut out due to osteoporosis and to evaluate its clinical outcome in these patients. Materials and Methods: In this prospective study, 30 patients aged 60 years and older with intertrochanteric fracture were included. Bone mineral density was measured. After reaming of the femoral head and neck with a triple reamer and polymethyl methacrylate, bone cement was introduced into the femoral head using a customized nozzle and a barrel fitted on a cement gun. A Richard screw was inserted and the plate was fixed over the femoral shaft. Patients were mobilized and clinical outcomes were rated using the Salvati and Wilson's scoring system. Results: More patients included in this study were between 66 and 70 years old than any other age group. The most common fracture according to the Orthopaedic Trauma Association classification was type 31A2.2 (46.7%). The T-score was found to be $-2.506{\pm}0.22$ (mean${\pm}$standard deviation); all patients were within the range of -2.0 to -2.8. The duration of radiological union was $13.67{\pm}1.77$ weeks. Salvati and Wilson's scoring at 12 months of follow up was $30.96{\pm}4.97$. The majority of patients were able to perform their normal routine activities; none experienced implant failure or screw cut out. Conclusion: Bone cement augmentation may effectively prevent osteoporosis-related hardware complications like screw cut out in elderly patients experiencing intertrochanteric fractures.

• Journal of Industrial Technology
• /
• v.30 no.A
• /
• pp.59-68
• /
• 2010

This study intended to examine the changes of residential building characteristics in period classification. The results of this study are as follows: During Joseon dynasty, it is judged that the social changes in the ideology of ruling classes did not directly affect the traditional residential style. The mid period and latter period of Joseon, it is changed toward horizontal and practical residential layout in place of confucian courtesy based style. During port opening period, the traditional residential style was remodeled through addition of glass panes to inter-chamber floor in tune with the influx of modern materials and ideologies like glass or cement etc. The Japanese ruling era of Korea period, the modern housing style of room separation type was settled.

• Journal of Korean Neurosurgical Society
• /
• v.43 no.6
• /
• pp.288-293
• /
• 2008

Objective : Bone cement leakage is a well-known potential complication of percutaneous vertebroplasty (PVP) in patients with osteoporotic compression fracture. Even though there has been a controversy in the efficacy of antecedent venography to prevent this complication, many authors have performed intra osseous venography before bone cement injection. The goal of this study was to classify the venous drainage patterns of spine before PVP, and compare their patterns at different vertebral levels. Methods : The authors retrospectively reviewed 1,042 intraosseous venographic patterns in 321 patients with 574 osteoporotic compression fractures during six-year period in one institution. To classify venogram patterns, we selected simple lateral X-ray of spine taken immediately after injection of the contrast dye. We classified the venography patterns according to contrast leakage pattern and leakage direction as follows; trabecular (TR), trabecular anterior (TA), trabecular posterior (TP), trabecular anterior-posterior (TAP), trabecular lateral (TL), venous anterior(VA), venous posterior (VP), venous anterior-posterior (VAP), soft tissue (ST). Also, we compared venogram patterns according to different spinal levels. Results : In overall, the most common pattern was TP type accounting for 37.4% (390/1042) of all intraosseous venograms. This is followed by TAP in 21.5%, TR 17.4%, TA 116%, TL 5.8%, ST 4.1%, VA 1.2%, VP 0.6%, and VAP 0.4% in descending order of frequency. According to the spinal level, TR and TAP types were most common in thoracic spine (T6-T10), TP type was most common in thoraco-Iumbar spine (T11-L2), and TP and TAP types were most common in lumbo-sacral spine (L3-S1). Contrast dye leakage to soft tissue such as psoas muscle or disc were detected in 43 (4.1%) venograms. Direct venous drainage without staining of vertebral body was found in 23 (2.2%) venograms. The 8.3% of thoracic venogram showed direct venous drainage. Thoracic level showed a more tendency of direct venous drainage than other spine levels (p<001). Conclusion : The authors propose a new classification system of intra osseous venography during PVP. The trabecular-posterior (TP) type is most common through all spine, and venous-filling (V) type was most frequent in thoracic spine. Further study would be necessary to elucidate the efficacy of this classification system to prevent bone cement leakage during PVP.

• Journal of Korean Foot and Ankle Society
• /
• v.23 no.2
• /
• pp.58-66
• /
• 2019

Purpose: To evaluate the efficacy of antibiotic-loaded cement spacers (ALCSs) for the treatment of diabetic foot infections with osteomyelitis as a salvage procedure and to analyze the risk factors of treatment failure. Materials and Methods: This study reviewed retrospectively 39 cases of diabetic foot infections with osteomyelitis who underwent surgical treatment from 2009 to 2017. The mean age and follow-up period were $62{\pm}13years$ and $19.2{\pm}23.3months$, respectively. Wounds were graded using the Wagner and Strauss classification. X-ray, magnetic resonance imaging (or bone scan) and deep tissue cultures were taken preoperatively to diagnose osteomyelitis. The ankle-brachial index, toe-brachial index (TBI), and current perception threshold were checked. Lower extremity angiography was performed and if necessary, percutaneous transluminal angioplasty was conducted preoperatively. As a surgical treatment, meticulous debridement, bone curettage, and ALCS placement were employed in all cases. Between six and eight weeks after surgery, ALCS removal and autogenous iliac bone graft were performed. The treatment was considered successful if the wounds had healed completely within three months without signs of infection and no additional amputation within six months. Results: The treatment success rate was 82.1% (n=32); 12.8% (n=5) required additional amputation and 5.1% (n=2) showed delayed wound healing. Bacterial growth was confirmed in 82.1% (n=32) with methicillin-resistant Staphylococcus aureus being the most commonly identified strain (23.1%, n=9). The lesions were divided anatomically into four groups; the largest number was the toes: (1) toes (41.0%, n=16), (2) metatarsals (35.9%, n=14), (3) midfoot (5.1%, n=2), and (4) hindfoot (17.9%, n=7). A significant difference in the Strauss wound score and TBI was observed between the treatment success group and failure group. Conclusion: The insertion of ALCSs can be a useful treatment option in diabetic foot infections with osteomyelitis. Low scores in the Strauss classification and low TBI are risk factors of treatment failure.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.553-556
• /
• 2008

This study analyzed is to investigate the effect of the combined use of fly ash and coarse particle cement(RCC) collected in particle classification method during ordinary portland cement(OPC) on the fundamental properties of concrete. Totally 16 batches of the concrete was fabricated vary the contends of FA and RCC. As results of experiment, in the case of flow, the more the contents of RCC, the larger the flow. And the more the contents of FA displacement rate increased, the less the flow. As for simple adiabatic temperature rise due to the RCC and FA contents, it decreased with the increase of them. And particularly in the case of RCC 30% + FA 30%, temperature rise amount, was very low. Compressive strength decreased in proportion to increase of the contents of FA and RCC. And strength ratio of the concrete incorporating FA and RCC for plain concrete at 28 days was 88%${\sim}$98%, which was relatively good results.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.889-892
• /
• 2008

This study, having combined and displaced fly ash known as admixture material that delays hydration reaction with coarse particle cement("CC" hereinafter) collected in particle classification method during ordinary portland cement("OPC" hereinafter), reviewed the hydration heat characteristics affecting the concrete. To reduce hydration heat, the study plain-mixed which used 100% OPC for WB 50% level 1, displaced CC at level 3 of 25%, 50% and 75% for OPC, and by displacing FA with admixture material at level 5 of 0%, 10%, 20%, 30% and 40%, experimented totally 16 batches. As a result of experiment, in the case of flow, the more CC displacement rate increased, the more it tended to decrease, and the more FA displacement rate increased, the more it decreased. As for simple adiabatic temperature rise by the CC and FA displacement rates, it decreased as displacement rate increased, and particularly in the case of FA40, temperature rise amount, $5.8{\sim}7.4^{\circ}C$, was very low. Compressive strength decreased in proportion to displacement rate, however strength reduction increment was shown to decrease with age progress.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.10 no.1
• /
• pp.104-114
• /
• 2000

This study was carried out to estimate current status of dust concentrations in the factories producing non-metallic products in Korea. Data were gathered from the environmental monitoring reports by 40 workplace environmental monitoring institutes and the questionnaire designed for the study by the authors. A total of 1838 dust samples from 368 plants were obtained from the reports and were analyzed with no data modifications. But data on asbestos, rock wool, and welding fumes were excluded in this evaluation. The factories were classified into eight groups according to the standard industrial classification scheme in Korea. The results of this study were as follows; 1. The factories included were glass, non-refractory ceramic, refractory ceramic ware, structural non-refractory clay and ceramic, cement and lime, articles of concretes, and stone. Mean(geometric mean) concentrations of total dust samples ranged from $1.75(0.84)mg/m^3$ to $5.87(2.84)mg/m^3$. Statistically significantly higher dust concentrations were found in the cement and lime industries compared with other industries. 2. The non-compliance rates were 15.2% in glass and 20.6% in other non-metallic mineral products industries. Although all institutions surveyed utilized the identical sampling and classification scheme for dusts as specified in the current occupational exposure limits, wide discrepancies were found in collecting samples and classifying dusts. Further problems were discovered in classifying dusts. A dust sample collected could be classified into any of the three groups regardless of silica content. The results of this study showed that dust concentrations in the non-metallic products industries varied widely. Also discovered was classification errors of dust types among workplace monitoring institutes. These errors could adversely affect the results of exposure assessments and the true nature of dust hazards. Further, no institutions performed respirable dust sampling and analysis of crystalline silica. In order to correct these malpractices, current standards of occupational exposure limits should be revised and tight supervision by the Ministry of Labour be suggested.

• Structural Engineering and Mechanics
• /
• v.68 no.6
• /
• pp.691-700
• /
• 2018

Ground granulated blast furnace slag (GGBS) is a by product obtained from iron and steel industries, useful in the design and development of high quality cement paste/mortar and concrete. This paper investigates the applicability of relevance vector machine (RVM) based regression model to predict the compressive strength of various GGBS based concrete mixes. Compressive strength data for various GGBS based concrete mixes has been obtained by considering the effect of water binder ratio and steel fibres. RVM is a machine learning technique which employs Bayesian inference to obtain parsimonious solutions for regression and classification. The RVM is an extension of support vector machine which couples probabilistic classification and regression. RVM is established based on a Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. Compressive strength model has been developed by using MATLAB software for training and prediction. About 70% of the data has been used for development of RVM model and 30% of the data is used for validation. The predicted compressive strength for GGBS based concrete mixes is found to be in very good agreement with those of the corresponding experimental observations.

• Land and Housing Review
• /
• v.15 no.1
• /
• pp.147-156
• /
• 2024

This study aims to reduce CO₂ generated during the manufacturing process by using limestone (CaCO₃), a carbonate mineral used in the production of cement clinker, as a decarbonated raw material that does not contain CO₂. Among various industrial by-products, we attempted to use cement paste attached to waste concrete. In general, limestone for cement must have a CaCO₃ content of at least 80% (CaO, 44% or more) to ensure the quality of cement clinker. However, the CaO content of waste concrete fine powder is about 20% on average, so in order to use it as a cement clinker raw material, the CaO content must be increased to more than 35%. Therefore, by using the difference in hardness of the mineral composition of waste concrete fine powder to selectively crush CaO type minerals with relatively low hardness, classify and sieve, the CaO content can be increased by more than 35%. Accordingly, in this study, we experimentally and statistically reviewed and analyzed the optimal conditions for efficiently separating CaO and SiO₂ and other components by selectively pulverizing minerals containing relatively low CaO through a grinding process. As a result of the optimal grinding conditions experiment, it was found that the optimal conditions were a grinding time of less than 5 minutes, a type of material to be crushed of 30 mm, and an amount of material to be crushed of 1.0 or more. However, it is judged that it is necessary to review pulverized materials of mixed particle sizes rather than pulverized products of single particle size.

• Steel and Composite Structures
• /
• v.36 no.6
• /
• pp.657-669
• /
• 2020

This study investigates the fire resistance characteristics of reactive powder concrete according to changes in the cement content per unit area, mixing ratio of metakaolin (MK), and content of polypropylene fiber. A fire test was conducted, and the resulting residual strength characteristics were investigated through flexural and compressive strength measurements, as well as condition rating classification based on visual evaluation. MK effectively reduced the initial high content of calcium hydroxide, thereby reducing the water vapor pressure generated during pyrolysis and slowing spalling. Furthermore, the pore structure and loose tissue were effective for relieving the water vapor pressure in the event of a fire.