• Nuclear Engineering and Technology
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• 제56권3호
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• pp.922-932
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• 2024

This paper presents the design features and preliminary design analysis results of the Wielenga Innovation Static Salt Reactor (WISSR). The WISSR incorporates features that make it both flexible and inherently safe. It is based on innovative technology that controls a nuclear reactor by moving molten salt fuel into or out of the core. The reactor is a low-pressure, fast spectrum transuranic (TRU) burner reactor. Inherent shutdown is achieved by a large negative reactivity feedback of the liquid fuel and by the expansion of fuel out of the core. The core is made of concentric, thin annular fuel chambers containing molten fuel salt. A molten salt coolant passes between the concentric fuel chambers to cool the core. The core has both fixed and variable volume fuel chambers. Pressure, applied by helium gas to fuel reservoirs below the core, pushes fuel out of a reservoir and up into a set of variable volume chambers. A control system monitors the density and temperature of the fuel throughout the core. Using NaCl-(TRU,U)Cl₃ fuel and NaCl-KCl-MgCl₂ coolant, a road-transportable compact WISSR core design was developed at a power level of 1250 MWt. Preliminary neutronics and thermal-hydraulics analyses demonstrate the technical feasibility of WISSR.

• Wind and Structures
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• 제8권6호
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• pp.443-454
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• 2005

Wind loading is very important, even dominant in some cases, to large-span single-layer reticulated shells. At present, usually equivalent static methods based on quasi-steady assumption, as the same as the wind-resistant design of low-rise buildings, are used in the structural design. However, it is not easy to estimate a suitable equivalent static wind load so that the effects of fluctuating component of wind on the structural behaviors, especially on structural stability, can be well considered. In this paper, the effects of fluctuating component of wind load on the stability of a single-layer reticulated spherical shell model are investigated based on wind pressure distribution measured simultaneously in the wind tunnel. Several methods used to estimate the equivalent static wind load distribution for equivalent static wind-resistant design are reviewed. A new simple method from the stability point of view is presented to estimate the most unfavorable wind load distribution considering the effects of fluctuating component on the stability of shells. Finally, with comparisive analyses using different methods, the efficiency of the presented method for wind-resistant analysis of single-layer reticulated shells is established.

• 대한기계학회논문집B
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• 제21권2호
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• pp.195-201
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• 1997

Static and non-static flame methods were used to measure the laminar burning velocity of methane, ethane and natural gas. The flame slot angle and velocity of unburned gas mixture were determined by Schlieren method and LDV, respectively, for static flame. The diameter of nozzle was selected as 11 mm. The experimental results containing the stretch effect showed that the maximum burning velocities were 41.5 for natural gas, 40.8 for methane and 43.4 cm/sec for ethane on equivalence ratio of 1.1. Constant volume combustion chamber was also used for non-static flame. The propagation process of flame front was visualized by high speed camera during constant pressure. The maximum burning velocity of natural gas was determined as 42.1 cm/sec on equivalence ratio of 1.15.

• The Journal of Korean Physical Therapy
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• 제28권5호
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• pp.274-278
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• 2016

Purpose: This study investigated changes in static balance during eye movement while in an upright standing position and compared static balance in elderly individuals according to age. Methods: A total of 154 elderly persons (male 23, female 136) were enrolled in the study. Participants followed an eye movement program that consisted of randomly occurring pursuit eye movement and saccadic eye movement. Participants were asked to remain in the double-leg standing position for 2 minutes 30 second while fixating their eyes on a specific target, after which they were instructed to perform eye movements for 2 minutes and 30 seconds. Static balance was measured in terms of the area, length, and average speed (cm/s) of the center of pressure (COP) displacement before and after eye movement intervention with the eyes open. Results: The area, length, and velocity of COP displacement improved significantly (p< 0.01) after intervention. No significant differences among age groups were observed. Conclusion: The results indicated that eye movement was an effective intervention for improving static balance in elderly persons.

• The Journal of Korean Physical Therapy
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• 제29권3호
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• pp.142-144
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• 2017

Purpose: Few studies have addressed the effect of diurnal circadian rhythms on postural stability, and thus the aim of the present study was to examine circadian effects on static and dynamic postural stability in young adults. Methods: Twenty-four subjects (9 men, 11 women: age=$22.20{\pm}1.77$, height=$167.20{\pm}10.47$, weight=$59.85{\pm}10.66$) from a university community volunteered for this study. Static and dynamic balance testing, which recorded using a Good Balance system (Good Balance, Metitur Ltd, Finland) was conducted at 9:00, 13:00, and 17:00 hours on two consecutive days, and the sequencing of static and dynamic balance tests were randomized. Results were analyzed using the non-parametric one-way repeated Friedman test in SPSS version 18.0 (SPSS Inc., Chicago, IL, USA), and variable found to be significant were subjected to Wilcoxon post hoc testing. Results: Static and dynamic balance showed significant difference at the three times assessments (test at 9:00, 13:00, and 17:00) during circadian. In the post hoc test of static (anteroposterior distance, mediolateral distance and COP (center of pressure) velocity) and dynamic balance (performance time), 13:00 was the longer and faster than 9:00. Conclusion: These results indicated that control of postural balance is influenced by diurnal circadian rhythms, and confirm that control of postural balance is more effective and better performance in the 09:00 hours than 13:00 hours or 17:00 hours.

• 한국산업융합학회 논문집
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• 제8권3호
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• pp.135-141
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• 2005

The static friction coefficients of 4 samples against each different temperatures were similar values. Compared against RT, at $80^{\circ}C$ the static friction coefficients decreased from 0.130 to 0.116 that was equal from 88% to 90% of the static friction coefficients respectively. Otherwise the dynamic friction coefficients compared against RT, decreased from 0.138 to 0.088 which was from 71% to 77.5% respectively at $80^{\circ}C$. The noise characteristics were judged by s/d value. And when the s/d value was limited less than 0.8, noise concerns were released. At 3000 engaging cycles the static friction and the dynamic friction coefficient were 0.137 and 0.073 respectively. When plate pressure rose up to $195kg_f/cm^2$, the static friction coefficient decreased from 0.137 to 0.125 but this decreasing could be considered as stable. When speed rose up to 2200rpm, the static friction coefficient decrease from 0.14 to 0.13 but this decreasing could be considered as stable. At 3000 engaging cycles the amount of worn out was 0.04 : the thickness of disc was decrease from 4.72mm to 4.68mm. But regarding the normal operation condition, further more worn-out could not be expected. Therefore concerning worn-out, the basic oil could be considered as appropriate.

• Geomechanics and Engineering
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• 제36권3호
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• pp.247-258
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• 2024

Tailings are waste materials of mining operations, consisting of a mixture of clay, silt, sand with a high content of unrecoverable metals, process water, and chemical reagents. They are usually discharged as slurry into the storage area retained by dams or earth embankments. Poor knowledge of the hydro-mechanical behaviour of tailings has often resulted in a high rate of failures in which static liquefaction has been widely recognized as one of the major causes of dam collapse. Many studies have dealt with the static liquefaction of coarse soils in saturated conditions. This research provides an extension to the case of silty tailings in unsaturated conditions. The static liquefaction resistance was evaluated in terms of stress-strain behavior by means of monotonic triaxial tests. Its dependency on the preparation method, the volumetric water content, the void ratio, and the degree of saturation was studied and compared with literature data. The static liquefaction response was proved to be dependent mainly on the preparation technique and degree of saturation that, in turn, controls the excess of pore pressure whose leading role is investigated by means of the relationship between the -B Skempton parameter and the degree of saturation. A preliminary interpretation of the static liquefaction response of Stava tailings is also provided within the Critical State framework.

• 한국화재소방학회논문지
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• 제30권2호
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• pp.56-61
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• 2016

최근 건축물은 대형화, 고층화되어 화재발생시 소방대의 활동이 제한되어 화염 및 연기에 의한 인명피해가 증가할 수 있다. 이러한 인명피해를 저감하기 위하여 제연설비가 필수적이며 특별피난계단 부속실 및 비상용승강기 승강장에 급기가압제연설비를 적용하고 있다. 국가 화재안전기준에서는 부속실 및 승강장과 거실과의 차압을 40 Pa 이상 요구하고 있으나 실제 현장에서는 과도한 과압이 다수 발생하고 있다. 이러한 과압의 원인은 댐퍼의 누설량의 과다에 의한 것으로 알려져 있다. 과압은 피난자의 문개방을 어렵게 하여 피난을 불가능하게 할 수 있다. 이러한 문제점을 확인하고자 자동차압 과압조절형댐퍼의 개폐 동작횟수 증가에 따른 누설량을 측정하여 초기에 공급된 댐퍼의 누설량과 비교 분석하였다. 실험결과 초기 제품과 반복동작 후 누설량의 차이가 발생했으며 정압이 증가함에 따라 누설량 차이가 증가되었다. 선행연구와 비교분석한 결과도 정압에 따른 선형적 증가의 경향이 유사한 추세를 보이고 있다.

• 대한정형도수물리치료학회지
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• 제28권3호
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• pp.41-49
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• 2022

Background: In patients with forward head posture (FHP), the head is positioned forward, causing increased tension in the muscles and structures of the head, neck, and shoulders. This can result in joint dysfunction that may lead to abnormal afferent information. The purpose of this study was to investigate the effect on foot pressure through the isometric hip abduction (IHA) bridge exercise using elastic bands in patients with FHP. Methods: Twenty patients with FHP were randomly assigned to a study group that applied joint mobilization, soft tissue mobilization, a deep neck flexor strengthening exercise, and the IHA bridge exercise using an elastic band. A control group was also constituted, and members were given joint mobilization, soft tissue mobilization therapies, and the deep neck flexor strengthening exercise. Ten patients were assigned to each group. The static foot pressure and dynamic foot pressure of each patient were measured before and after the intervention, and the interventions for each group were applied twice a week for 4 weeks. Results: Both the study group and the control group showed significant differences in static and dynamic foot pressure before and after the interventions (p<.05). There were no significant differences in foot pressure between the study and control groups. Conclusion: : The results of this study revealed that there were no significant differences between the group doing the IHA bridge exercise using the elastic band and the control group. However, the intervention methods applied to both the groups were effective in improving the body center control of FHP patients.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.2168-2173
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• 2003

Pressure balancing valve is one of important control devices, which is fully automatic and no manual controls, regulating or adjustments are needed. It is typically used to maintain constant temperature of working fluid in power and chemical plants and domestic water supply systems. Pressure balancing valve is composed of body, cylinder and balancing piston. Therefore, the balancing piston shapes are important design parameters for a pressure balancing valve. In this study, numerical and experimental analyses are carried out with two different balancing piston shapes. Especially, the distribution of static pressure is investigated to calculate the flow coefficient($C_v$). The governing equations are derived from making using of three-dimensional Navier-Stokes equations with standard ${\kappa}-{\varepsilon}$ turbulence model and SIMPLE algorithm. Using commercial code, PHOEIC, the pressure and flow fields in pressure balancing valve are depicted.