• Fire Science and Engineering
• /
• v.23 no.5
• /
• pp.50-56
• /
• 2009

Explosion limit and autoignition temperature are the major properties used to determine the fire and explosion hazards of the flammable substances. Explosion limit and autoignition temperature for safe handling of ethylene were investigated. By using the literatures data, the lower and upper explosion limits of ethylene recommended 2.6vol% and 36vol%, respectively. Also autoignition temperatures of ethylene with ignition sources recommended $420^{\circ}C$ at the electrically heated crucible furnace (the whole surface heating) and recommended about $800^{\circ}C$ in the local hot surface. The new equations for predicting the temperature dependence and the pressure dependence of the lower explosion limits for ethylene are proposed. The values calculated by the proposed equations were a good agreement with the literature data.

• Earthquakes and Structures
• /
• v.26 no.1
• /
• pp.31-48
• /
• 2024

In order to get a better understanding of seismic performance of exterior beam-column joint, reciprocating loading tests with variable loading speeds or axial forces were carried out. The main findings indicate that only few cracks exist on the surface of the joint core area, while the plastic hinge region at the beam end is seriously damaged. The damage of the specimen is more serious with the increase of the upper limit of variable axial force. The deflection ductility coefficient of specimen decreases to various degrees after the upper limit of variable axial force increases. In addition, the higher the loading speed is, the lower the deflection ductility coefficient of the specimen is. The stiffness of the specimen decreases as the upper limit of variable axial force or the loading speed increase. Compared to the influence of variable axial force, the influence of the loading speed on the stiffness degradation of the specimen is more obvious. The cumulative energy dissipation and the equivalent viscous damping coefficient of specimen decrease with the increase of loading speed. The influence of variable axial force on the energy dissipation of specimen varies under different loading speeds. Based on the truss model, the biaxial stress criterion, the Rankine criterion, the Kent-Scott-Park model, the equivalent theorem of shearing stress, the softened strut-and-tie model, the controlled slip theory and the proposed equations, a calculation method for the shear capacity is proposed with satisfactory prediction results.

• PNF and Movement
• /
• v.3 no.1
• /
• pp.27-34
• /
• 2005

Objective : The purpose of this study was conducted to find correct head and neck patterns, manual contact. verbal commands with proprioceptive neuromuscular facilitation(PNF). Method : This is a literature study with books, seminar note and book for PNF international course. Result : Keep the information of the biomechanics and neural science in head and neck patterns and emphasize that manual contact, verbal commands and visual stimulus. Manual contacting for movement guide and stability of the $C_0/C_1$ verbal command and visual stimulus for correcting of the $C_0/C_1$ movements. Conclusion : In reminder for PNF learning, begin with head and neck and upper trunk patterns. In that time, Knott and Voss(1968) had not enough information about biomechanic movement components and neural science movement components. But Knott and Voss(1968) emphasized that head and neck patterns relate with trunk, upper extremities and lower extremities directly. Alar ligaments are relaxed with the head in neutral and taut in flexion. Axial rotation of the head and neck tightens both alar ligaments. The right upper and left lower portions of the alar ligament limit left lateral flexion of the head and neck. Therefore, head and neck patterns has to be modify. When head moving, eye and vestibular stimulus will be change. During head and neck patterns, must be consider about stimulus of eye system and vestibular system also.

• The Korean Journal of Quaternary Research
• /
• v.33 no.1_2
• /
• pp.59-68
• /
• 2021

The maximum upper limit of seawater inflow can be recognized by the acid-resistant dinoflagellate cysts and salt-marsh pollen encountered from surface samples in the lower reach of Jujin Stream facing Gomso Bay. Based on their relative yield ratio, the downstream area of Jujin Stream could be further subdivided into coastal marine, brackish-upper limit brackish, and freshwater environments. The abundance of dinoflagellate cysts from JJR-41 to JJR-36 sites reflects that this area is a coastal marine. In the section between JJR-35 and JJR-5 sites, dinoflagellate cysts associated with pollen derived from riparian or salt-marsh (e.g., reeds and sedges) appear to reflect the brackish environments. It may be indicated that dinoflagellate cysts appear up to the JJR-4 site, which is the maximum upper limit where seawater flows up to this point at high tide. This analysis is relatively well corresponding to the hypothetical inundation map showing the maximum flooding area where seawater can flow at high tide.

• Earthquakes and Structures
• /
• v.16 no.4
• /
• pp.437-453
• /
• 2019

This study investigates a new optimal placement method for viscous dampers between structures in order to prevent pounding of adjacent structures with different dynamic characteristics under earthquake effects. A relative displacement spectrum is developed in two single degree of freedom system to reveal the critical period ratios for the most risky scenario of collision using El Centro earthquake record (NS). Three different types of viscous damper design, which are classical, stair and X-diagonal model, are considered to prevent pounding on two adjacent building models. The objective function is minimized under the upper and lower limits of the damping coefficient of the damper and a target modal damping ratio. A new algorithm including time history analyses and numerical optimization methods is proposed to find the optimal dampers placement. The proposed design method is tested on two 12-storey adjacent building models. The effects of the type of damper placement on structural models, the critical period ratios of adjacent structures, the permissible relative displacement limit, the mode behavior and the upper limit of damper are investigated in detail. The results of the analyzes show that the proposed method can be used as an effective means of finding the optimum amount and location of the dampers and eliminating the risk of pounding.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.35 no.4
• /
• pp.439-444
• /
• 2011

To determine the test gases for gas appliances of new gas group, the interrelation between gas interchangeability, including thermal efficiency, of 13A gas appliances and present 13A test gases was experimentally investigated. The test results show that the Wobbe indices in the case of incomplete combustion and the flame lifting limit gas for the new gas group are respectively 2% higher than the upper limit and 1% lower than the lower limit of the Wobbe index range. The most suitable composition of R gas is 96 mol% of methane and 4 mol% of propane; LNG could be also used as R gas. Further, analysis results showed that the hydrogen concentration of flash back limit gas could be lowered from 30 vol% to 23 vol%.

• Journal of Nutrition and Health
• /
• v.8 no.4
• /
• pp.9-14
• /
• 1975

Growth retardation and a variable degree of body disproportion are recognized features of malnutrition, and mild and moderate protein-calorie malnutrition(PCM). Among the various body measurements suggested to assess the prevalence of all grades of PCM as judged by growth retardation and by body disproportion, the 'mid-upper-arm circumference'-abbreviated to 'arm-circumference' has been suggested as a potential useful simple field index for the assessment of PCM showing that the measurement would give composite information simultaneously on three important effects on PCM-deficit in the muscle protein reservoirs, availability of calorie stores in the form of subcutaneous fat, and growth failure. And this is selected because of its easy accessibility, and less involvement with clinical edema. This study is conducted to make a comparison between the percentage of Korean weight for age standards and the percentage of mid-upper-arm circumference for age standards of 175 preschool children aged $3{\sim}72$ months who are selected among the low-income residents in Seoul. In this study, a comparison is made between the results obtained by expressing the observed weight of the child as a percentage of Korean standard, referred to as 'weight-for-age' and the observed arm-circumference expressed as a percentage of the age-specific arm standard of Jelliffe, referred to as 'arm-for-age'. All the measurements were taken following the techniques described by Jelliffe. The left mid upper arm was measured using a glass-fibre tape and the Fairbanks Morse beam balance was used for weighing. 80% level of weight for age Korean standard and 85% level of arm for are Jelliffe standard were used as an upper borderline limit for PCM. Comparing the 80% weight-for-age and the 85% arm-for-age standard as an upper limit for PCM, for children aged $3{\sim}72$ months, results in 84.6% agreement with the sensitivity of 86.4% and its specificity of 83.5%. If arm circumference alone had been measured and judgement made on this basis, then only 5.1% of the children would have been 'wrongly' classified. And there is a moderately close correlation between arm circumference and weight for age as the data in Table 4 shows. The problem therefore lies in the standard for arm circumference in normal children and in determining what is the lower limit of normal. Once this is clearly difined, one can rely more confidently on arm circumference measurements alone for the nutritional assessment of early childhood.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.11a
• /
• pp.357.1-357
• /
• 2002

The purpose of this study is to propose indoor noise level in residential buildings affected by transportation noise (road traffic, railway and air-craft noise) based on subjective evaluations. 30 subjects participated in the experiment to evaluate the noise. Experimental environment reproduced real living and office environment, and in asking subjects' annoyance to the noise. (omitted)

• Journal of Advanced Marine Engineering and Technology
• /
• v.12 no.1
• /
• pp.37-45
• /
• 1988

A calculating method of transient temperature distribution due to spot welding of thin plates is studied in this paper. Considering the contact stress between upper and lower plate and temperature-dependence of specific resistance and elastic limit of base metal, the model of calorific density of heat source was decided. Using 2-dimensional polar coordinates system, the governing equation of heat transfer was developed. The thermal cycles of various points were recorded using C-A thermocouples during spot welding procedure for mild steel plates of 1mm thickness, and those results were compared with the results of calculations presented in this paper.

• Communications of the Korean Mathematical Society
• /
• v.38 no.2
• /
• pp.389-400
• /
• 2023

In this paper, some estimations will be given for the analytic functions belonging to the class 𝓡(α). In these estimations, an upper bound and a lower bound will be determined for the first coefficient of the expansion of the analytic function h(z) and the modulus of the angular derivative of the function ${\frac{zh^{\prime}(z)}{h(z)}}$, respectively. Also, the relationship between the coefficients of the analytical function h(z) and the derivative mentioned above will be shown.