• Journal of the Korean GEO-environmental Society
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• v.23 no.8
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• pp.11-16
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• 2022

The compaction process using vibrating rollers in road construction is essential to increase soil stiffness in earthworks. Currently, there is no clear standard for the operation method of the compaction roller during compaction. Although simple quality inspection techniques have been developed, plate load test (PLT) and field density test (FDT) are the most frequently used test methods to evaluate the degree of compaction during road construction as the most frequently used quality inspection methods. However, both inspection methods are inefficient because they cannot perform quality inspection in all sections due to time and cost reasons. In this study, we analyzed how the operating conditions of vibrating rollers affect the compaction quality. An intelligent quality management system, which is a currently developed and commercialized technology, was used to obtain quality inspection results in all sections. As a result of the test, it was analyzed that the speed and vibration direction of the compaction roller had an effect on the compaction degree, and it was found that the compaction direction had no effect on the compaction degree.

• Research in Community and Public Health Nursing
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• v.6 no.2
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• pp.319-334
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• 1995

To investigate the risk factors of low back pain, an epidemiological study was carried out among male workers aged 20-55 employed in an automobile industry in Korea during the time period from February 1993 to October 1995. Workers participated to this study were divided into low back pain group(LBP) and control group, according to the self-reports by written questionnaires. General characteristics, medical history, work related factors, fatigue, and MMPI were compared between two groups. To clarify the relationship between job related low back pain and radiologic features of lumbar spine, radiographic study was carried out. The resultant data were processed for $x^2-test$, t-test, and stepwise logistic regression to confirm the adjusted odds ratios. The results were as follows: 1. History of back disease, lifting and carrying work, excessive physical fatigue, and weakend back strength of individual workers were directly associated with low back pain. Odd ratios of these 4 risk factors of low back pain were 5.07, 3.34, 1.49, and 1.22 respectively. 2. The frequency of low back pain history was significantly higher in LBP group. 3. Back muscle strength of lumbar spine of LBP group were significantly lower than control group. 4. The workers in LBP group revealed high fatigue symptoms. 5. In MMPI test LBP group showed higher scales in hypochondriasis, depression, hysteria, psychopathic deviate, paranoia, psychasthenia, schizophrenia, and hypomania. 6. LBP group were more frequently involved in lifting and carrying, working in awkward position, bending, twisting and using lower extremities. 7. LBP group were exposed more to vibration during working. 8. In the Analysis of radiographs of lumbar spine, Jacob's line not crossing fourth lumhar disc space, transitional vertebrae and lumbar displacement more than 4.4mm in standing lateral view were more frequently observed in LBP group than control group. Through these results, it is concluded that identification of previous history of back problem, change of work or working environment for workers with previous back problem and measures to relieve both physical and psychological fatigue of the workers are required for optimal management of work-related back problems among workers. In the present study, several results were different from the previous reports: Jacob's line not corssing fourth lumbar disc space, lumbarization, and vertebral slipping (spondylolisthesis) more than 4.4mm are related to backache. Meticulous studies are required to elucidate the difference.

• Explosives and Blasting
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• v.32 no.2
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• pp.16-24
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• 2014

In this "Wonju~Jaecheon double-lanes railroad" project, a highway is located at about 13meter above a tunnel. Initially, rock-splitting method was used for the tunnel excavation in order to minimize the possible damage on the highway. The method, however, takes a long time for the tunnel excavation and that may cause other problems like large displacement of tunnel and subsidence of highway ground before the tunnel can be stabilized by supporters. Therefore, the application of electronic blasting method(eDdevII) was recommended to control the blast vibration below 1.0cm/sec as well as to prevent the subsidence of highway ground. The analysis of the influence of tunnel excavation on the highway showed that electric blasting method is permissible for the safe management of the highway. Based on that, the tunnel construction under a highway could be carried out quickly and safely without any damages on the highway.

• Journal of the Korean Society of Safety
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• v.30 no.4
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• pp.128-134
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• 2015

The number of schools which have passed 30 years after the construction takes up 30% (5% falling to class D and E) in Korea. So, the offices of education across the nation conduct large works for the expansion, improvement and renovation of the school. But as the work takes a lot of time, the work is also conducted while the students are studying at the schools. The work at the school causes the noise, dust, vibration as the school often has the reinforced concrete structure. So, as the windows are closed to prevent the nuisance from hampering the education, the problems related to the illumination, ventilation, and control of humidity and temperature are give damages to students studying the school buildings. Actually, as the current renovation or expansion is conducted across the nation due to the implementation of the new education system and the resulting integration and construction of hub school, specialized school, meister school and it causes a lot of nuisance to the learning students and others, there are a lot of complaints from concerned people. Accordingly this study suggests the method of evaluating the factors which affect the learning environment such as the noise, dust or fine dust and reducing the nuisances to the level proper for the learning environment when the existing school is expanded, improved or renovated.

• Journal of Korean society of Dental Hygiene
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• v.4 no.2
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• pp.225-236
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• 2004

It has been suggested in research results thai dental hygienists have high risk of carpal tunnel syndrome, mainly caused by the repeated motion of extensor and flexor or the use of vibration tools, compared to other occupations. To find out the situation of the carpal tunnel syndrome of dental hygienists, who are exposed to work-related musculoskeletal disorders, this study used 132 questionnaires given on May 22, 2004, the period of continuing education of the first half year in the Gwangju Jeonnam area, and obtained the following results. 1. Subjects worked at a dental ciinic(32.6%), a hospital(31.8%), and a public health center(35.6%). Age by work was under 24 in a clinic(17.4%) and a hospital(15.9%), and over 30 in a public health center(35.6%). 2. In practice conducted over one time a day, a scaling accounted for 90.7% in a doctor's office; 595% in a hospital; and 3.0% in a public health center, suggesting significant difference(p<0.01). Pit and fissure sealant accounted for 53.5% in a clinic; 53.2% in a hospital; and 95% in a public health center, also suggesting significant difference(p0.01). 3. Symptoms of carpal tunnel syndrome appeared in a wrist(12.1%), a right hand(14.4%), and a left hand(5.3%). 4. In case of temporary crown practice, symptoms appeared in a wrist(22.0%), a right hand(14.0%), and a left hand(4.0%), suggesting significant difference(p<0.01). The above results showed that 12.1% of dental hygienists was exposed to carpal tunnel syndrome. Thus, it is considered very important that dental hygienists should be given education of the danger of continuous work in certain motions and prevention education of improving repeated position, and make efforts to reinforce self-control ability.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.8
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• pp.1241-1246
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• 2013

Currently, The general transportation system arranges the armature on the full length of transportation lines. However, when this method is applied to the long distance transportation system, it causes an increase of material cost and manufacturing time. Thus, in order to resolve this problem, discontinuous arrangement method of the armature has been proposed. However, in the method of using stationary discontinuous armatures, mover can stop in the freewheeling section which is non-installations section when disturbance is generated and the mover can not be moved because armature control is impossible. Thus, the distance determination of armature is very important. Also, when the armature is arranged discontinuously the edge always exists due to the structure. Due to this edge, the cogging force is greatly generated during the entry and ejection of the mover to the armature. This cogging force causes thrust force ripple generating noise, vibration and decline of performance, it must be reduced. Therefore, in this paper, we examined the end edge cogging force generated by the stationary discontinuous armatures through 2-D numerical analysis using finite element method (FEM) and we figured out distance of armature for end edge cogging force minimization.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.5
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• pp.396-404
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• 2015

The UAV's wing has high aspect ratio that is suitable for the high altitude and long endurance. Knowing the real-time deformation of wing structure in flight, it can be utilized in structural health and loading status monitoring, improvement of control effectiveness and extraordinary vibration phenomena using displacement-strain relationship. In this paper, nonlinear displacement prediction algorithm was developed for prediction of large structural deflection in flight. The algorithm was validated through the comparison with finite element analysis results and also experimental results for several large tip displacements of cantilever beam. The predicted displacements using strains are agreed well with the measured values from laser displacement sensor.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.735-737
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• 2015

In this paper, SaaS (Software as a Service) based transport and construction process safety management systems by utilizing the construction work process management and safety management and schedule, and results for various types of construction process, achieved through high-speed wireless Internet access by applying to ensure a systematic means for safety and can quickly and accurately manage all made within the process control system. The operator should be indicated by using a smart phone to work as a supervisor report the current status and results of the operation. Also be reported to the supervisor immediately in an emergency situation and there is no vibration occurs over a period of time the smartphone is to check the danger to the operator. If the commissioner is directed to specific business processes that establish and verify the results obtained and the result is satisfied by presenting the part down the measures insufficient command of the field workers risk situations. In the case of software (server) to store all the data relating to the operation member in charge of management and security.

• Wind and Structures
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• v.23 no.2
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• pp.109-125
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• 2016

Flow interference is investigated between two tripped cylinders of identical diameter D at stagger angle ${\alpha}=0^{\circ}{\sim}180^{\circ}$ and gap spacing ratio $P^*$ (= P/D) = 0.1 ~ 5, where ${\alpha}$ is the angle between the freestream velocity and the line connecting the cylinder centers, and P is the gap width between the cylinders. Two tripwires, each of diameter 0.1D, were attached on each cylinder at azimuthal angle ${\beta}={\pm}30^{\circ}$, respectively. Time-mean drag coefficient ($C_D$) and fluctuating drag ($C_{Df}$) and lift ($C_{Lf}$) coefficients on the two tripped cylinders were measured and compared with those on plain cylinders. We also conducted surface pressure measurements to assimilate the fluid dynamics around the cylinders. $C_D$, $C_{Df}$ and $C_{Lf}$ all for the plain cylinders are strong function of ${\alpha}$ and $P^*$ due to strong mutual interference between the cylinders, connected to six interactions (Alam and Meyer 2011), namely boundary layer and cylinder, shear-layer/wake and cylinder, shear layer and shear layer, vortex and cylinder, vortex and shear layer, and vortex and vortex interactions. $C_D$, $C_{Df}$ and $C_{Lf}$ are very large for vortex and cylinder, vortex and shear layer, and vortex and vortex interactions, i.e., the interactions where vortex is involved. On the other hand, the interference as well as the strong interactions involving vortices is suppressed for the tripped cylinders, resulting in insignificant variations in $C_D$, $C_{Df}$ and $C_{Lf}$ with ${\alpha}$ and $P^*$. In most of the (${\alpha}$, $P^*$ ) region, the suppressions in $C_D$, $C_{Df}$ and $C_{Lf}$ are about 58%, 65% and 85%, respectively, with maximum suppressions 60%, 80% and 90%.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.198-201
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• 2001

Porous structures of aluminum foam have been studied by using return aluminum scrap. The apparent foam shape, foam height, density, pore size and their distributions in various section areas of the experimental samples have been investigated. The sample have been cast into metallic mold, using aluminum foam prepared from a precursor based on pure Al ingot and return aluminum scrap mixed with various amounts of 1-2wt% increasing viscosity and foam agent materials. The process provides for flexibility in design of foam structures via relatively easy control over the amount of hydrogen evolution and the drainage processes which occur during foam formation. This is facilitated by manipulating parameters such as the foaming agent, thermal histories during solidification and mix melt viscosities. A metal for producing the foamed are decomposing a foaming agent in a molten metal such that there is an initial and a subsequent expansion due to foaming agent. It has been found that the Al porous foaming with variation amount of 1∼2wt% foam agent and at 2min holding time, which melting temperature has appeared homogeneous pore size at 650∼700$^{\circ}C$. The compression strength were 10-13 kg/min at 125ppi, and increased by higher pore density. The acoustical performance of the panel made with the foamed aluminum is considerably improved; its absorption coefficient shows NRC 0.6-0.8. It has been found that the Al foam is very preferable for the compactness of the thermal system.