• 열처리공학회지
• /
• 제31권2호
• /
• pp.56-62
• /
• 2018

Many researchers have studied on the precipitation control after solution treatment to improve the damping capacity without decreasing the strength. However, studies on the damping capacity and microstructure changes after deformation in the solid solution strengthening alloys were inadequate, such as the Al-Zn series magnesium alloys. Therefore, in order to investigate the effect of annealing condition on microstructure change and damping a capacity of AZ61 magnesium alloy. In this study, it was confirmed that the microstructure changes affect the damping capacity and hardness when annealed AZ61 alloy. AZ61 magnesium alloy was rolled at $400^{\circ}C$ with rolling reduction of 30%. These specimens were annealed at $350^{\circ}C$ to $450^{\circ}C$ for 30-180 minutes. After annealing, microstructure was observed by using optical microscopy, and damping capacity was measured by using internal friction measurement machine. Hardness was measured by Vickers hardness tester under a condition of 0.3 N. In this study, static recrystallization was observed regardless of the annealing conditions. In addition, uniform equiaxed grain structure was developed by annealing treatment. Hardness is decreased with increasing grain size. This is associated with Hall-Petch equation and static recrystallization. In case of damping capacity, bigger grain size show the larger damping capacity.

• Geomechanics and Engineering
• /
• 제22권5호
• /
• pp.441-448
• /
• 2020

This paper presents a study on the undrained shear strength (s_u) of various sands treated with a biopolymer by employing an extensive series of laboratory fall-cone penetration values covered a range of about 15 mm to 25 mm. In the tests, two sizes (0.15 mm-0.30 mm, and 1.0 mm-2.0 mm) and shapes (rounded, angular) of sand grains, Xanthan gum (XG), and distilled water were used. The XG biopolymer in 0.0%, 1.0%, 2.0%, and 3.0% by dry weight were mixed separately with four different sands, and water. The tests results obtained at the same water content revealed an increase in the su values at different levels with an increase in the XG content. Treating the sands with the XG biopolymer addition was concluded to have a greater efficacy on finer and more angular grains than coarser and more rounded grains in the samples. Overall, the present study indicates that different amount of the XG biopolymer has an important potential to be utilized for increasing the s_u values of samples with various size/shape of sand grains and water content.

• The Journal of Asian Finance, Economics and Business
• /
• 제8권7호
• /
• pp.1-9
• /
• 2021

This paper investigates the impact of the domestic and global outbreak of the coronavirus (COVID-19) pandemic on the trading size of the Malaysian stock (MS) market. The theoretical model posits that stock markets are affected by their response to disasters and events that arise in the international or local environments, as well as to several financial factors such as stock volatility and spread bid-ask prices. Using daily time-series data from 27 January to 12 May 2020, this paper utilizes the traditional Augmented Dickey and Fuller (ADF) technique and Zivot and Andrews with structural break' procedures for a stationarity test analysis, while the autoregressive distributed lag (ARDL) method is applied according to the trading size of the MS market model. The analysis considered almost all 789 listed companies investing in the main stock market of Malaysia. The results confirmed our hypotheses that both the daily growth in the active domestic and global cases of coronavirus (COVID-19) has significant negative effects on the daily trading size of the stock market in Malaysia. Although the COVID-19 has a negative effect on the Malaysian stock market, the findings of this study suggest that the COVID-19 pandemic may have an asymmetric effect on the market.

• The Journal of Asian Finance, Economics and Business
• /
• 제8권7호
• /
• pp.517-523
• /
• 2021

Audit quality encompasses the key elements that create an environment that maximizes the likelihood that quality audits are performed consistently. This study aimed to identify the impact of auditing quality on the market value of the manufacturing companies listed on the Amman Stock Exchange (ASE). The analytical method was adopted in this research to extract and collect the necessary data. This study hypothesizes that audit quality leads to an increase in the market value by the offering of high-quality services. The study used the panel data approach to analyze cross-sectional data for 41 industrial companies that included time series data for the period (2019-2019). To test its hypotheses, the study used the fixed-effect model. The study found that the audit quality factors (audit office size, client retention period, auditor's fees, and linking with international audit offices) did not have a significant impact on market value. It found also the positive impact of the audit office size on the market value of the listed companies on the ASE for the period from 2009 to 2019. The study recommended the management of the company realize the importance of contracting with audit offices of large size and good reputation because these offices are more capable of increasing their efficiency, qualifying their employees, and thus be fully prepared for the audit process efficiently and effectively.

• Nuclear Engineering and Technology
• /
• 제55권11호
• /
• pp.4096-4101
• /
• 2023

Radon is a radioactive gas produced from the uranium-238 series. Radon gas affects public health and is the second cause of lung cancer. The study samples were collected from one area of the city of Jazan, southwest of the Kingdom of Saudi Arabia. The influence of engineering and physical parameters on the emanation coefficient of gas and other gas parameters was studied. Parameters for radon were measured using a CR-39 Solid-State Nuclear Track Detector (SSNTD) through a sealed emission container. The results showed that the emanation coefficient was affected directly by the change in the grain size of the soil. All parameters of measured radon gas have the same behavior as the emanation coefficient. The relationship between particle size and emanation coefficient showed a good correlation. The values of the emanation coefficient were inversely affected by the mass of the sample, and the rest of the parameters showed an inverse behavior. The results showed that increasing the volume of the container increases the accumulation of radon sons on the wall of the container, which increases the emission factor. The rest of the parameters of radon gas showed an inverse behavior with increasing container size. The results concluded that changing the engineering and physical parameters has a significant impact on both the emanation coefficient and all radon parameters. The emanation coefficient affects the values of the radiation dose of an alpha particle.

• 한국강구조학회 논문집
• /
• 제9권1호통권30호
• /
• pp.107-120
• /
• 1997

The purpose of this study is to develop composite structural system which is to have versatility in plan design and to improve economical efficieney, to maximise structural capacity than existing structural system. In this viewpoint, it was investigated to the properties of structural behaviors for i oint consisting of concrete filled steel square tube column and P.C reinforced concrete beam through a series of hysteretic behavior experiment. In the previous report, researched to the properties of joints with key parameters. such as Axial Force ratio and section types. From the based on previous results, this study investigated the properties of this joints with key parameters, such as strength of concrete, size of panel zone and Axial Force ratio. The obtained results are summarised as follows. (1) Investigating for the failure mode of the beam-to-column joint, the specimens of S,LL and LH series(except for L5H) presented flexural failure mode. (2) The initial stiffness of joint was increasd as the decrease of axial force ratio and increase of the concrete strength. (3) The rotation resisting capacity was effective as the increment of the concrete strength and decrement of the axial force ratio. (4) The emprical formula to predict the ultimate capacity of joint model to introduce decrease coefficient according to the axial force ratio to superimpose shearing strength of steel web(H section) and bending strength of reinforced concrete beam was expected.

• 한국분무공학회지
• /
• 제11권4호
• /
• pp.251-265
• /
• 2006

To prevent the ozonosphere from being destroyed by Halon, it is an urgent task to find out Halon replacement. As one of the replacements water mist have showed broad applications by its advantages: little pollution to environment (not destroying the ozone layer or bring green house effect), extinguishing fire quickly, consuming a small quantity of water and having little damage to the protected objects. The methods of generating water mist strongly influence fire suppression effectiveness, which determine the cone angle, drop size distribution, flux uniformity, and momentum of the generating spray. The traditional water mist nozzle included pressure jet nozzles, impingement nozzles and twin-fluid nozzles. All of them have more or less disadvantages for fire suppression. Therefore, many research institutes and corporations are taking up with innovations in mist generation. This article provided some recent studies in State Key Laboratory of Fire Science (SKLFS) of University of Science and Technology of China. SKLFS have investigated new methods of generating water mist (i.e. effervescent atomization and ultrasonic atomization). and self developed a series of nozzles and developed advanced DPIVS (Digital Particle Image Velocimetry and Sizing) technique. Characteristics of water mist (the distribution of droplet sizes, flux density, spray dynamics and cone angle) produced by these nozzles were measured under different conditions (work pressure, nozzle geometry, etc.) using LDV/APV and DPTVS systems. A series of experiments were performed to study the fire suppression effectiveness in different fire scenario (different kindsof the fuel, fire size and ventilation conditions). The fire extinguishing mechanisms of water mist was also discussed.

• 한국식생활문화학회지
• /
• 제28권1호
• /
• pp.31-40
• /
• 2013

The purpose of this study is to analyze external elements of 'time series table serving' and to discover any problems in the table setting. We selected two traditional Korean restaurants in five-star hotels and two representative traditional Korean style restaurants and analyzed the tableware arrangement of their table settings. The results are as follows. In restaurant A, the arrangement of different styles of tableware made from a variety of materials seemed relatively natural. However, the dessert plates were 'Buncheong' ware made with 'Bakji' method; in this case, the pattern was larger than the size of the fruits served and made the food inconspicuous. Rather than using plates made with a 'bakji' method, using plates with small patterns in the 'johwa' method would complement the food. In restaurant B, the space between the tableware, spoon and chopsticks was narrow, and the spoon and chopsticks sets would not fit on the table pads when large dishes or multiple dishes were served. In this case, changing the dishes to smaller sized dishes, considering the size of the table pad, or not using the pad at all would solve the issue. In restaurant C, too many small dishes were laid on the table, making it look disorderly. We believe that recovering tableware that is no longer in use, laying dishes and cutlery inside of the table pads or not using the table pad would be better. In restaurant D, the same style and color of dishes were provided 9 times. The lack of variety could be tedious to customers. The forms and colors of dishes should be changed in accordance with the order of the meal served. However, when using tableware created by different methods such as 'Buncheong' ware or white porcelain, the same pattern should be chosen in order to elevate the dignity of the table menu through uniformity. These issues in tableware arrangement indicate that external forms of banquet table setup should be studied so that the culture of Korean traditional cuisine can be enriched.

• 한국태양에너지학회 논문집
• /
• 제35권4호
• /
• pp.1-7
• /
• 2015

The operation of the natural circulation type solar heating systems with facade integrated collector was analyzed by experiment. Two different types of flat plate solar collectors were used for these experiments. One was for the normal flat plate solar collector with the size of 1m*2m and the other was for the large size solar collector with $4m^2$(1m*4m). The experiments were carried out to investigate the effect of the series or parallel connection method on the performance of the collectors. As a result, the solar thermal system which is installed on the wall or facade would be applicable for the natural circulation type if the system design reflects various parameters, including collector connecting method(series or parallel), to provide enough vertical height between collector and storage tank, and to reduce pressure loss due to collector and piping network, etc. The natural circulation type of solar thermal system as proposed in this study can increase the system reliability by removing or minimizing the use of the components such as pump, controller, sensors which may cause serious troubles of the system for a long-time operation

• KDI Journal of Economic Policy
• /
• 제30권2호
• /
• pp.1-26
• /
• 2008

본고에서 우리는 한국의 주택 부 효과의 크기를 재검토한다. 이를 위해 주택가격 상승에 대한 주택 보유자 소비지출의 반응인 '순수한' 주택 부 효과의 크기를 알아보는 데 중점을 둔다. 순수한 주택 부 효과를 측정하기 위해 거시시계열 자료를 이용할 경우, 주택 보유여부와 적절한 소비지출변수의 선정이라는 두 가지 문제가 제기된다. 우리는 먼저 비 주택 소비(non-housing consumption)가 보다 적절한 소비지출변수임을 보이며, 그 이유로 주택소비(housing consumption)의 상당 부분이 주택 보유자들의 실제로 지불하지 않는 귀속임대료(imputed rents)임을 제시한다. 이어서 우리는 거시시계열 자료로부터 구한 주택 부 효과의 크기를 얼마나 수정해야 주택보유자에의 순수한 주택 부 효과를 추정할 수 있는가를 살펴본다. 이를 위해 두 개의 구조적 모형을 설정하여, 전체 소비지출 중에서 주택 보유자 소비지출의 비중을 추정한다. 주택 보유자의 소비지출 비중을 감안하여 수정된 주택부의 효과는, 거시시계열을 이용하여 구한 통상적인 주택 부 효과의 추정치보다 크게 나타난다.