• Journal of Biomedical Engineering Research
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• v.44 no.5
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• pp.336-345
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• 2023

The present study was designed to evaluate changes in neuromuscular properties and the structural and qualitative characteristics of muscles during submaximal isometric contractions at low-to-relatively vigorous target forces and to determine their influence on force steadiness (FS). Thirteen young adult males performed submaximal isometric knee extensions at 10, 20, 50, and 70% of their maximal voluntary isometric contraction using their non-dominant legs. During submaximal contractions, we recorded force, EMG signals from vastus medialis (VM), vastus lateralis (VL), and rectus femoris (RF), and ultrasound images from the distal RF (dRF). Force and EMG standard deviation (SD) and coefficient of variation (CV) values were used to measure FS and EMG steadiness, respectively. Muscle thickness (MT), pennation angle (PA), echo intensity (EI), and texture features were calculated from ultrasound images to assess the structural and qualitative characteristics of the muscle. FS, neuromuscular properties, and texture features showed significant differences across different force levels. Additionally, there were significant differences in EMG_CV among the quadriceps at the 50% and 70% force levels. The results of correlation analysis revealed that FS had a significant relationship with EMG_CV in VM, VL, and RF, as well as with the texture features of dRF. This study's findings demonstrate that EMG steadiness and texture features are influenced by the magnitude of the target force and are closely related to FS, indicating their potential contribution to force output control.

• Journal of Drive and Control
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• v.21 no.1
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• pp.22-30
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• 2024

Gearboxes designed for reciprocating motion operating mechanisms operate under conditions where both the load and speed undergo continuous variations. When conducting durability tests on gearboxes designed for such applications, operating the target gearbox under conditions similar to the intended usage is essential. The gearbox must be operated for the required number of cycles to validate its durability under conditions mirroring its intended usage. This study devised an accelerated test method for gearboxes, which reduces operating angles and operational strokes. The reliability of the accelerated test was verified by comparing the stresses imposed on the gears under general and acceleration conditions through multi-body dynamic simulations. The results confirmed that the maximum contact stress levels under normal and accelerated conditions were within a 0.1% error range, indicating a minimal difference in the gear damage rates. However, a difference in the maximum contact stress results between the normal and accelerated conditions was observed when inertial forces acted on the output shaft due to the operational acceleration of the gearbox. Therefore, when conducting this acceleration test, caution should be exercised to ensure that the operational load on the gearbox, which affects inertia, does not significantly deviate from the conditions observed under normal operating conditions.

• Safety and Health at Work
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• v.14 no.4
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• pp.438-444
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• 2023

Background: To examine the influences of psychosocial work conditions on mental health risk and intention to leave the public sector among workers of public health agencies in Taiwan. Methods: We surveyed 492 public health workers in March 2022 during the COVID-19 pandemic. Information on job demands, job control, workplace justice, experiences of workplace violence and its type and origin, and mental health status (assessed by the 5-item Brief Symptom Rating Scale, BSRS-5) was obtained. Of them, 192 participated in a follow-up survey conducted in May 2023 that assessed mental health status, employment changes, and intention to leave. Results: In the initial survey, 32.93% of participants reported poor mental health status, defined by having a score of BSRS-5 ≧ 10, and 48.17% experienced some form of workplace violence over the past year. Notably, high psychosocial job demands (OR = 3.64, 95% CI = 1.93-6.87), low workplace justice (OR = 2.58, 95% CI = 1.45-4.58), and workplace violence (OR = 2.38, 95% CI = 1.51-3.77) were significantly associated with increased risk of mental disorders. Among those who participated in the followup survey, 22.40% had persistent poor mental health, and 30.73% considered leaving or have left the public sector. Longitudinal analyses indicated that job demands predicted persistent mental disorders and intention to leave the public sector, and the experience of workplace violence added additional mental health risks. Conclusion: The public health workforce is crucial for effective and resilient public health systems. Our findings that public health workers were at high mental health risk and had a high intention to leave the job warrant attention and policy interventions.

• Structural Engineering and Mechanics
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• v.91 no.1
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• pp.75-86
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• 2024

In this paper, the porous metal PM-35 is proposed as the filler material of filled thin-walled tubes (FTTs), and a series of experimental study is conducted to investigate the dynamic behavior and energy absorption performance of PM-35 filled thin-walled tubes under impact loading. Firstly, cylinder solid specimens of PM-35 steel are tested to investigate the impact mechanical behavior by using the Split Hopkinson pressure bar set (SHP); Secondly, the filled thin-walled tube specimens with different geometric parameters are designed and tested to investigate the feasibility of PM-35 steel applied in FTTs by the orthogonal test. According to the results of this research, it is concluded that PM-35 steel is with the excellent characteristics of high energy absorption capacity and low yield strength, which make it a potential filler material for FTTs. The micron-sizes pore structure of PM-35 is the main reason for the macroscopic mechanical behavior of PM-35 steel under impact loading, which makes the material to exhibit greater deformation when subjected to external forces and obviously improve the toughness of the material. In addition, PM-35 steel core-filled thin-wall tube has excellent energy absorption ability under high-speed impact, which shows great application potential in the anti-collision structure facilities of high-speed railway and maglev train. The parameter V0 is most sensitive to the energy absorption of FTT specimens under impact loading, and the sensitivity order of different variations to the energy absorption is loading speed V0>D/t>D/L. The loading efficiency of the FTT is affected by its different geometry, which is mainly determined by the sleeve material and the filling material, which are not sensitive to changes in loading speed V0, D/t and D/L parameters.

• SUVANNABHUMI
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• v.16 no.2
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• pp.185-211
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• 2024

Southeast Asian cities like Manila, the Philippines, and Singapore have witnessed economic, political, and cultural changes over the years, especially after periods of colonization. States control their urban fabric-that is, its organization, planning, and design of cities-and thus dictate the flow of capital and forces of labor. Urban poor settlements, an offshoot of capital accumulation, are (re)moved around these cities in accordance with governing visions of development. For populations that are forced into changes brought about by urban development, practices of remembering are also controlled by dominant powers. These "monuments" are established in/as spaces to oblige an image of membership into a society ruled by such powers. Nevertheless, alternate sites of remembering counter these monumental spaces. This paper takes an interest in two novels that feature such places. Liwayway Arceo's Canal de la Reina (1972) and Suchen Christine Lim's The River's Song (2013) both figure rivers in Manila and Singapore, respectively. The eponymous river is the central axis of Canal de la Reina, entangled in class conflict and swift urban change in post-Commonwealth Manila. In The River's Song, the famous Singapore River provides a refuge for reminiscing about Singapore before the city-state's independence. Comparing these novels to what Filipino comparatist Ruth Jordana Pison calls fictional "counter-memory," we argue that their rivers remember personal and embodied experiences eliminated from hegemonic accounts of the city. Thus, they function as what we call "counter-monuments" for the urban poor marginalized in the history of the Philippines and Singapore.

• Particle and aerosol research
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• v.20 no.2
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• pp.25-33
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• 2024

Suspension of particulate matter (PM) in indoor spaces, which increases risk of negative impact on occupants' health from exposure to PM, is influenced by humidity level in the indoor environment. The goal of this study is to investigate the property of size-resolved PM suspension in accordance with the relative humidity through simulation chamber experiments which reflect the indoor environmental characteristics. The relative humidity of simulation chamber is adjusted to 35%, 55% and 75% by placing it inside a real-size environmental chamber which allows artificial control of climatic conditions (e.g., temperature, humidity). At the respective humidity conditions, PM suspension concentration caused by occupant walking is analyzed by particle size (0.5-0.8, 0.8-1.0, 1.0-2.5, 2.5-3.5, 3.5-4.5, 4.5-5.5, 5.5-8.0, and 8.0-10 ㎛). Irrespective of the particle size, the suspension concentration reveals a decreasing tendency as the relative humidity increases. Furthermore, a one-way analysis of variance (one-way ANOVA) test statistically verifies that the suspension concentration has a significant difference depending on the indoor relative humidity level. In addition, as the relative humidity increases, a proportion of the suspended particles with 0.5-2.5 ㎛ diameter decreases, while that with 2.5-3.5 ㎛ diameter increases. The reason is considered that the humidity has an effect on adhesion and coagulation forces of the particles.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.347-358
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• 2009

Recently, it is getting into a good situation for the flat-plate slab system to be applied. The flat-plate slab without beam, however, is often too weak to control deflection properly compared to other typical slab-beam structures, for which the post-tension method is generally regarded as one of best solutions. The post-tension (PT) method can effectively control deflection without increase of slab thickness. Despite this good advantage, however, the application of PT method has been very limited due to cost increase, technical problems, and lack of experiences. Therefore, in order to reduce difficulties on applying full PT method under the current domestic circumstances and to enhance constructability of PT system, this research proposed the partial PT method with top jacking anchorage applied in a part of span as need. For the top jacking anchorage system, the efficiency of deflection control shall be considered in detail because it can vary widely depending on the location of anchorage that can be placed anywhere as need, and tensile stresses induced at back of the anchorage zone also shall be examined. Therefore, in this study, analysis were performed on the efficiency of deflection control depending on the location of anchorage and on tensile stresses or forces using finite element method and strut and tie model in the proposed top jacking anchorage system. The proposed jacking system were also applied to the floor slabs at a construction site to investigate its applicability and the analysis results of slab behavior were compared to the measured values obtained from the PT slab constructed by the partial PT method. The result of this study indicates that the partial PT method can be very efficiently applied with little cost increase to control deflection and tensile stresses in the region as a need basis where problem exists.

• The korean journal of orthodontics
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• v.28 no.2 s.67
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• pp.297-310
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• 1998

The purpose of this study was to investigate the initial tissue change, to repair on the teeth & surrounding tissue under the intrusive orthodontic forces by use of elastic chain, through the microscopic findings. For this study, three young adult mongrel dogs were used, and were divied into three group : the control group was deliveried only casting crown and the experimental group 1 was equipped with energy chain during 1 week and experimental 2 group was deliveried using energy chain during 1 week and 3 weeks observation. All experimental groups and control groups were sacrificed to make the samples for microscopic findings on premolar teeth. All samples were examed and compared the histologic changes through the microscopic with H-E stain. The obtained results were as follows. 1. In hematoxylin-eosin stain of the control group, the periodontal ligament was constant width from apical third to cervical third of the root, and the periodontal fiber arrangement was horizontal or oblique in cervical third, oblique in middle and apical third of the root. 2. In Masson Trichrome stain of the control group, osteoblast and osteoclast appeared in cervical third of root, and bone resorption and new bone formation was observed in middle and apical third of the root. 3. In experimental 1, osteoclasts were increased highly, and hyperemia of blood vessels and new bone formation and bone resorption by reversal line in apical third of the root were seen. PDL width was increased apprarently from crest to apex of the root and more in apical third. 4. In experimental 2, osteoclasts and hyperemia of blood vessels were more increased than control material in apical third of the root. PDL width was increased more than control group in root apex, and was seen less than experimental 1. PDL arrangement was similar to experimental 1 and was mixed only in root apex. Therefore, in premolar intrusion of the young adult dog, there were increased osteoclast, hyperemia and dilation of blood vessel, resorption of alveolar bone and cementum and different arrangement of PDL in initial tissue change. There was not observed complete repair after remove intrusive force.

• Journal of the Korean Association of Geographic Information Studies
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• v.18 no.4
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• pp.14-30
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• 2015

This paper attempted to analyze the hydraulic effects that the dredging can take as an alternative to reduce possible damages of flooding due to the overflow of river levee in meandering rivers, where riverbed aggradation, seepage and erosion may occur. In order to make a hydraulic analysis in a section of meandering rivers, a two-dimensional hydraulic analysis model, RMA-2, was selected. The GIS was applied to construct two-dimensional finite element grids to consider the hydraulic conditions before and after dredging. The water surface elevations, depths, velocities, and tractive forces were compared before and after the dredging. The difference of water surface elevation between the inside and outside of river was turned out to be the maximum value of 0.58m under the design flood condition. It could be evaluated that the tractive force at the bank decreased about 42 to 67% on average for all the sections. These results could give valuable information that the dredging of the stream channel at the meandering sections decreased the risk of overflow, seepage and erosion of the banks. The methodologies given in this study will contribute to mitigating the flood damages in the surrounding farmlands.

• The korean journal of orthodontics
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• v.26 no.4
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• pp.341-348
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• 1996

The efficiency of maxillary canine retraction by means of sliding mechanics along an 0.016 continuous labial arch and an 0.009 inch in diameter with a lumen of 0.030 inch NiTi closed coil spring was compared with that using the same NiTi closed coil spring and Molar Anchoring Spring(MAS) which was designed by author. MAS was made of .017" X .025" TMA wire and was given 60 degree tip-back bend on the wire close to the molar tube. This study was designed to investigate molar and canine root control during retraction into an extraction site with continuous arch wire system. Two techniques were tested with a continuous arch model embedded in a photoelastic resin. A photoelastic model was employed to visualize the effects of forces applied to canine and molar by two retraction mechanics. With the aid of polarized light, stresses were viewed as colored fringes. The photoelastic overview of the upper right quadrant showed that stress concentrations were observed in its photoelastic model. The obtained results were as follows. 1. Higher concentration of compression can be seen clearly at the distal curvature of the canine and mesial curvature of the molar and premolar when NiTi closed coil spring was applied only, which means severe anchorage loss of the molar and uncontrolled tipping of the canine. 2. The least level compression was presented at the mesial root area of the molar and premolar, and mesial root area of the canine when NiTi closed coil spring and MAS were used simultaneously. Especially mesial alveolar crest region of the canine was shown moderate level of compression that means MAS can be used as a appliance for anchorage control and prevention of canine extrusion and uncontrolled tipping during canine retraction.