• Earthquakes and Structures
• /
• 제14권3호
• /
• pp.241-248
• /
• 2018

To study the mechanical properties of joints in ancient timber buildings in depth, the force mechanism of the through-tenon joints was analyzed, also the theoretical formulas of the moment-rotation angles of the joints with different loosening degrees were deduced. To validate the rationality of the theoretical calculation formulas, six joint models with 1/3.2 scale ratio, including one intact joint and five loosening joints, were fabricated and tested under cyclic loading. The specimens underwent the elastic stage, the plastic stage and the destructive stage, respectively. At the same time, the moment-rotation backbone curves of the tenon joints with different looseness were obtained, and the theoretical calculation results were validated when compared with the experimental results. The results show that the rotational moment and the initial rotational stiffness of the tenon joints increase gradually with the increase of the friction coefficient. The increase of the tenon section height can effectively improve the bearing capacity of the through-tenon joints. As the friction coefficient of the wood and the insertion length of the tension increase, the embedment length goes up, whereas it decreases with the increase of section height. With the increase of the looseness, the bearing capacity of the joint is reduced gradually.

• Journal of Welding and Joining
• /
• 제21권3호
• /
• pp.40-45
• /
• 2003

The high-speed rotating arc process forms a flat bead surface with decreased penetration depth because the molten droplets are deflected by centrifugal force. Therefore the rotating arc welding for horizontal fillet welding increases the leg length with the increase of rotation frequency and prevents the deflection of weld bead and overlap. In this study, the relationship between the welding parameters and the weld bead shape - leg length and undercut - are investigated experimentally. Consequently, the weld quality could be improved by rotating arc welding, and sound weld bead was achieved when applied to horizontal fillet welding with 4mm gap by avoiding the undercut which is inevitable for the conventional GMA welding methods.

• Korean Journal of Childcare and Education
• /
• 제9권2호
• /
• pp.117-141
• /
• 2013

The purpose of this study is to investigate the young children's 'more means more' bias and knowledge change process regarding a lever phenomenon, especially the relationship between the weight of an object and the strength of force and between the length of a lever and the strength of force. Subjects, who were presented with the tasks, were eight young children 5 years of age. Major findings were as followings. First, most of the subjects have a 'more means more' bias about the relationship between the weight of an object and the strength of force and between the length of a lever and the strength of force regarding a lever phenomenon. This meant that young children have similar concepts about a lever phenomenon regardless of whether it is right or wrong physically. Second, young children tried to make sure of their knowledge during experiments. They chose the evidence which confirmed their knowledge. But they tried to change their knowledge, when the evidence presented did not correspond to their knowledge. These findings contribute to understanding young children's 'more means more' bias and knowledge change process about a lever phenomenon and can be used in preschool science education programs and curriculums.

• The korean journal of orthodontics
• /
• 제44권1호
• /
• pp.20-27
• /
• 2014

Objective: The aims of this study were to evaluate the relationship between the detachment force and bonding resin surface are and to determine the resin bonding surface area that would provide adequate bonding strength with minimum resin volume. Methods: One hundred and sixty human premolars were randomly divided into 4 groups of 40 teeth each. The diameter of the resin surface area in each group was as follows: group 1, 1.5 mm; group 2, 2.5 mm; group 3, 3.5 mm; and group 4, 4.5 mm. Respond Dead Soft straight (length 0.0175 inch) was used to fabricate the retainers, and $Transbond^{TM}$ XT was used to fix the retainers to the tooth surfaces. A pair of teeth was embedded in acrylic blocks for each specimen. Thus, each group comprised 20 samples. Fixed retainers were bonded to the teeth, and vertical force was applied at the middle of wire. The force was measured using a universal testing machine. Results: The mean value of detachment force was the highest for group 4 ($102.38{\pm}2.92N$), followed by group 3 ($63.54{\pm}2.21N$), group 2 ($51.95{\pm}1.61N$), and group 1 ($24.14{\pm}1.38N$). Conclusions: The detachment force of lingual fixed retainers was significantly affected as the area of the resin bonding surface increased. Considering the minimum bonding strength of brackets, a resin bonding surface area with a diameter of 3.5 mm would provide adequate bonding strength.

• Journal of Biomedical Engineering Research
• /
• 제41권2호
• /
• pp.84-93
• /
• 2020

Despite of a lot of studies about proprioception tests, there are little study results to investigate the relationship between the functional movement and proprioception level. In this study, we tried to perform quantitative analysis for the effect of ankle joint proprioception level on the one leg standing postural control ability. Nine healthy people volunteered for this study. Force and position aspects of proprioception were evaluated using the electromyography system (EMG) and mobile clinometer application, respectively. The center of pressure (COP) trajectories, measured by a pressure mat sensor, were used for quantitative analysis of balance for each subject. We computed indices and errors of force and position aspects of proprioception from the EMG and ankle angle. Mean velocity of total and anterior-posterior direction (Vm and Vm_ap), root mean squared distance in anterior-posterior direction (RDap), travel length (L), and area (A) of COP trajectories were also calculated as indices of postural control ability of subjects. Two aspects of proprioception showed the low correlation from each other as previous studies. However, the EMG error of gastrocnemius lateral activation showed a high correlation coefficient with COP variables such as Vm (ρ=0.817, p=0.007), Vm_ap (ρ=0.883, p=0.002), RDap (ρ=0.854, p=0.003), L (ρ=0.817, 0.007) and A (ρ=0.700, p=0.036). Within our knowledge, this is almost the first study that investigated the relationship between proprioception level and functional movement. These study results could support that the ankle joint proprioception facilitation exercise would have positive effects on functional balance rehabilitation interventions.

• Steel and Composite Structures
• /
• 제21권5호
• /
• pp.1031-1043
• /
• 2016

Optimization of the construction scheme of the cable-strut tensile structure based on error sensitivity analysis is studied in this paper. First, the element length was extracted as a fundamental variable, and the relationship between element length change and element internal force was established. By setting all pre-stresses in active cables to zero, the equation between the pre-stress deviation in the passive cables and the element length error was obtained to analyze and evaluate the error effects under different construction schemes. Afterwards, based on the probability statistics theory, the mathematical model of element length error is set up. The statistical features of the pre-stress deviation were achieved. Finally, a cable-strut tensile structure model with a diameter of 5.0 m was fabricated. The element length errors are simulated by adjusting the element length, and each member in one symmetrical unit was elongated by 3 mm to explore the error sensitivity of each type of element. The numerical analysis of error sensitivity was also carried out by the FEA model in ANSYS software, where the element length change was simulated by implementing appropriate temperature changes. The theoretical analysis and experimental results both indicated that different elements had different error sensitivities. Likewise, different construction schemes had different construction precisions, and the optimal construction scheme should be chosen for the real construction projects to achieve lower error effects, lower cost and greater convenience.

• Journal of Family Resource Management and Policy Review
• /
• 제25권2호
• /
• pp.41-52
• /
• 2021

The purpose of this study is to examine how female labor force participation, family policies, and gender equality are related to fertility rate across countries. Multiple measures has been collected from various data sources(such as OECD, UNDP, and WVS) and the panel data set which includes (mostly) OECD countries range from 1990 to 2019 are analyzed. The major findings are as follows. First, based on OECD countries samples, female labor force participation is positively associated with the fertility rate, which implies that women's labor force participation does not lead to a reduction in fertility rate. Second, the length of paternity leave is positively associated with fertility rate whereas the direction is the opposite for the relationship between the length of maternity leave and fertility rate. This is attributed to the possibility that a longer period of maternity leave incurs the a higher opportunity cost of earning income, which leads to a reduced fertility rate. Third, countries with higher gender inequality index tend to have a higher fertility rate. Similarly, countries with higher gender equality value have a lower fertility rate. When the gender equality value is devideed into three sub-categories, education, politics, and employment, the gender equality value in education is the only sub-category which is negatively associated with the fertility rate. This study confirms that female labor force participation may not be a contributing factor in the lowering of fertility rate but instead can be positively associated with the fertility rate. Also, the results show that family policies or gender equality values can be significantly affect fertility rate.

• Korean Journal of Agricultural Science
• /
• 제9권2호
• /
• pp.569-575
• /
• 1982

Mechanical properties of rice plants were tested to determine compressive force, bending force, tensile force and shear force for improvement of harvesting machines and for efficient utilization of rice culm during the proper harvesting period. Rice varieties used in this study were two Japonica varieties with Irri 348 and Jinju, and two $Indica{\times}Japonica$ hybrids with Seogwang and Taebaeg, which were grown in the standard fertilization field of Chungnam Rural Development Office. Also Jinju and Taebaeg were tested to elucidate the shearing characteristics which included shear force-strain relationship, shear force and shear energy according to the position from the ground level, the shearing angle to the rice culm, and the moisture content. 1. Compressive force, bending force, tensile force and shear force were higher In Japonica varieties than $Indica{\times}Japonica$ hybrids. 2. Shear force to overall culm length decreased progressively to upper positions in Jinju variety but a constant shear force was approximately showed between the ground level and the position of 21cm in Taebaeg variety. 3. Shear force and shear energy increased with increase of the cross sectional area, and the rates of increase were high in general up to the cross sectional area of $10mm^2$ and then they became dull very much. 4. Shear force and shear energy decreased with decrease of moisture content of rice culm after cutting up to the moisture content of 60% (w. b.) and then they did not change significantly.

• Korean Journal of Breeding Science
• /
• 제43권4호
• /
• pp.311-317
• /
• 2011

This experiment was conducted to give basic information to sprout-soybean breeding and automated sprout production by investigating the effect of seed size on the sprout growth and texture. Twenty cultivars and lines including large and medium soybean, small interspecific cultivars and extra-small wild soybean lines were used. Seeds were cultured for 4 days using small sprout-culturing kits. Hypocotyl length of large Hwanggeumkong, small Pungsannamulkong and Soyoung were longer and wild soybean lines were shorter than other cultivars. Fresh sprout weight and growth rate per unit dry seed weight of wild soybean lines ware increased dramatically and more than other cultivars between 48 to 72 hours after culture. Not only the increasing rate but sprout yield ratio to used dry seed weight showed the negative relationship pattern with seed size. The hardness of hypocotyl in Jangyeubkong, mastication in Taekwang, and cutting force in Eunhakong were the highest as 3,505 g, 1,650 g, and 133 g respectively, and texture values of these traits in wild soybean YWS516 were the lowest. Cutting force of soybean hypocotyl showed the positive relationship pattern with seed size. Breaking force of hypocotyl in large Jangyeobkong was the highest as 83.5g and wild soybean lines were the lowest showing the same pattern as other textural characters.

• Korean Journal of Agricultural Science
• /
• 제31권2호
• /
• pp.115-122
• /
• 2004

Physical and mechanical properties of fruits of jujube (Zizyphus jujuba Miller), leaves, secondary branches, and leafy stems were measured and analyzed. The physical dimensions of the fruits were measured and the detachment force of the fruit and leafy stems was measured. The detachment force of the jujube fruits increased and the force-to-weight ratio of the jujube fruits decreased as the weight of the jujube fruit increased. The weight of the leafy stems, number of leaves attached to the leafy stems, length of the leafy stems, diameter of the stem side of the leafy stems, diameter of the leafy stem end was average of 0.7g, 6.6ea, 12.2cm, 4.5mm, and 2.7mm, respectively. The major and minor axis of the jujube leaves, area of leaves, weight of the leaves, and detachment force of the leaves was average of 5.7cm, 3.3cm, $12.98cm^2$, 0.20g, and 4.39N, respectively. The terminal velocity of the jujube fruits increased as the weight of the fruits increased. The terminal velocity of the leafy stems, however, did not show a relationship with the weight of the leafy stems and the number of leaves attached to the leafy stem. The terminal velocity, however, slightly increased as the length of the leafy stems increased.