• Geotechnical Engineering
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• v.7 no.1
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• pp.7-14
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• 1991

Determination of dynamic shear modulus of soil was made by measuring directly the velocity of ultrasonic shear waves transmitted through the specimen. The PUNDIT, a generator and detector of ultrasonic waves, has been used to measure the propagation velocity. Forty -six tests of compacted soil at seven different void ratios and seven varying degrees of saturation with four types of materials were made in this study. The primary importance in this study was the investigation of the relations among the para meters which influenced G-modulus, As a results of analysis, the dynamic shear modulus of soil tends to decrease with an increase of void ratio, and also it is affected by soil types. In case of using PUNDIT, the proper range of the specimen length is from 5cm to 8cm. And the degree of saturation doesn't affect the dyn- amic shear modulus of soil.

• Journal of the Korean Wood Science and Technology
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• v.25 no.3
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• pp.8-15
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• 1997

The ultrasonic velocity and dynamic MOE of acetylated bamboos were investigated using PUNDIT, a transit time measuring device for longitudinal ultrasonic propagation. Bamboo specimens were boiled in acetic anhydride for 2, 4 and 6 hours, and the maximum average WPG (Weight Percentage Gain) of 19% was obtained at 6 hours. The volumes of acetylated bamboos increase with boiling time and WPG, while as WPG increases their oven-dry densities generally increase with a concave around 5% WPG. This oven-dry density pattern likely influences the trends of ultrasonic velocity and dynamic MOE. which generally decrease with a convex around 5% WPG. It is postulated that during boiling extractives in a bamboo move and aggregate at its surfaces transiently, resulting in the increase of ultrasonic velocity and dynamic MOE. To explain the fact that ultrasonic velocity varies with WPG a simple model was proposed and some ultrasonic properties of a transmitted wave were examined.

• The Journal of Asian Finance, Economics and Business
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• v.5 no.2
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• pp.63-72
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• 2018

Researches based on the pattern of planned behavior holds that the three variables of entrepreneurial attitudes, subjective norms, and perceived behavior control influence each other and influence entrepreneurial intentions respectively. However, there are also different, even conflicting research conclusions that continue to emerge. Researches based on the pattern of alertness, believe that profit opportunities and individuals' pursuit to truth are the driving forces. Many scholars have demonstrated the impact of individual entrepreneurial alertness on entrepreneurial intentions. However, as an exogenous causal agent, profit opportunities have a logical problem: if there are no other assumptions, the mere existence of opportunities does not adequately explain entrepreneurial alertness. To address this gap, this study considered samples from mainland China, where entrepreneurial activities are very active currently, to test the role that entrepreneurial alertness is assumed to play in the planned behavior model. The results show that the three dimensions of alertness, individually partly intermediate the influence of entrepreneurial attitude on entrepreneurial intention, the influence of subjective norms on entrepreneurial intention, and that of perceived behavior control on entrepreneurial intention. This article studied the production of entrepreneurial intention by integrating the two patterns of planned behavior and alertness through empirical analysis, and opened up a new field for subsequent research on entrepreneurial intention.

• The Journal of Asian Finance, Economics and Business
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• v.6 no.1
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• pp.205-215
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• 2019

Researchers have confirmed the relationship between ambidexterity learning and innovation performance, but according to the resource-based theory, the relationship between ambidexterity learning and innovation performance is also affected by the internal resources of the organization. Internal resources are an important factor affecting the transformation of learning outcomes into performance. In addition, few scholars have pointed out whether different types of learning have different effects on different types of innovation performance. This study collects data from 170 High-tech enterprises in Shandong, china, and discusses the effects of exploitative learning and explorative learning on management innovation performance and technological innovation performance. This study further examines the moderating role of slack resource on the relationship between ambidexterity learning and innovation performance. Results show that ambidexterity learning has positive effect on innovation performance. Compared with exploitative learning, explorative learning has a greater impact on management innovation performance; compared with explorative learning, exploitative learning has a greater impact on technological innovation performances. Slack resource has positive moderating role between the relationship of exploitative learning, explorative learning and technology innovation performance. But Slack resource has no moderating role between the relationship of exploitative learning, explorative learning and management innovation performance.

• Journal of the Korean Wood Science and Technology
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• v.27 no.1
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• pp.50-55
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• 1999

Since ultrasonic stress wave velocity varies with wood temperature and moisture content, ultrasonic stress wave could be a tool to predict wood moisture content if temperature effect could be eliminated. This temperature effect was investigated by measuring the velocities of ultrasonic stress waves transmitting through air, a metal bar and a dimension lumber at various temperatures. For air the velocity and amplitude of the ultrasonic stress wave increase with temperature, while for a metal bar and a dimension lumber those decrease as temperature increases. However all three materials showed velocity hystereses with a temperature cycle. The effect of temperature and moisture content on stress wave velocity of a dimension lumber was depicted in the form of a three dimensional graph. The plot of stress wave velocity vs. wood moisture content was well fitted by two regression equations: a exponential equation below 46% and a linear equation above 46%.

• Journal of Electrical Engineering and Technology
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• v.2 no.3
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• pp.300-305
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• 2007

This paper reports an investigation of overvoltages caused by ferroresonance in the distribution system, which consists of a bank of open-delta single-phase voltage transformers. The high voltage sides of the voltage transformer are connected to the distribution system via three single-phase fuse cutouts. Due to the saturation characteristic of the transformer cores, ferroresonance can occur in the condition that the transformer is energized or deenergized with single-phase switching operation of the fuse cutouts. The simulation tool based on EMTP is used to investigate the overvoltages at the high side of voltage transformer. Bifurcation diagrams are used to present the ferroresonance behavior in ranges of different operating conditions. The simulation results are in good agreement with the results from the experiment of 22 kV voltage transformers. The mitigation technique with additional damping resistors in the secondary windings of the voltage transformers will be introduced. Brief discussion will be made on the physical phenomena related to the overvoltage and the damage of voltage transformer.

• Journal of the Korean Wood Science and Technology
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• v.39 no.2
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• pp.117-124
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• 2011

The possibility of using the properties of an ultrasonic wave as a means for monitoring the moisture content of a board during drying was investigated. The ultrasonic wave signals are influenced by moisture content and other factors such as temperature, moisture gradient and coupling area. The effect of temperature was examined by measuring the transit times, amplitudes and velocities of ultrasonic waves transmitted through air, a metal bar and a board at various temperatures. The effect of a moisture gradient was studied using a model specimen composing five wood pieces of various moisture contents. The velocity and amplitude of the ultrasonic waves transmitted through air increase with temperature, while those through a metal bar and a board decrease. It was confirmed that the temperature effect is partially attributed to the change of transducer's properties. The effect of a moisture gradient on the velocity of an ultrasonic wave varies with the average moisture content of a board. As the dimension of the end face of a board increases the velocity of an ultrasonic wave increases and low frequency components more dominates than high frequency components. The transit times of ultrasonic waves transmitted through a board during kiln drying reflect the temperature steps in the drying schedule and the transducer temperatures.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.9
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• pp.1-9
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• 2021

This study aimed to investigate the existence of the Feldstein-Horioka (1980) puzzle in international macroeconomics by applying the conditional Autoregressive Distributed Lag (ARDL) model to examine the long-run relationship between national savings and investments in Thailand and China. The input of this study relied on annual national savings and investments as a fraction of GDP during 1980-2019 which was collected from China National Bureau of Statistics (NBS) and Thailand National Economic and Social Development Council (NESDC). Hypothetically, Augmented Dickey-Fuller (ADF) and Phillips-Perron (PP) unit root tests were applied to test the stationary properties and to investigate the integration level of selected time series. The empirical results, confirmed by cumulative sum (CUSUM) and cumulative sum square (CUSUMSQ), maintained no serial correlation and structural break problems. The finding of this study suggested that the Feldstein-Horioka puzzle in Thailand did not exist significantly. Thailand's national savings and investments nexus was independent, following the classic economic idea that financial liberalization, or perfect capital mobility, allowed national savings and investments to flow freely to countries with better interest rates. Whereas, a strong significant correlation was found in the case of China during the fixed exchange rate regime switching in 1994 and post WTO participation after 2001-2019.

• Journal of the Korean Wood Science and Technology
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• v.36 no.1
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• pp.61-68
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• 2008

The effect of rupture on the speed of ultrasonic wave was investigated with the PUNDIT and the effective detecting method of defects, moving transmitter and receiver. The speed of ultrasonic wave according to the course of rupture was not affected by transmitter and receiver and in the course of parallel rupture, but only in the course of vertical rupture. When rupture was not located on the ultrasonic wave progressing course, rupture was not detected. However, if rupture was formed perpendicularly to the ultrasonic wave progressing course but located on the ultrasonic wave progressing direction, rupture can be detected. Also, the rupture can be detected, when one transmitter and receiver was placed at top and the other at bottom. After detecting rupture in a part, rupture was determined accurately, placing and moving two transmitters and receivers at width.

• 한국지구물리탐사학회:학술대회논문집
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• 2008.10a
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• pp.201-206
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• 2008

Determining the coefficient of weathering(CW) for stone heritage plays very important role in investigation and conservation plan. In most case, CW is obtained from the empirical relation, which use the difference between sonic velocities of fresh and weathered rocks. In this paper, we measured sonic velocities for the samples from Iksan, Geochang, Wonju, Goesan and Chungju of which our stone heritages are made. We first investigate the uncertainty of velocity by portable measurement by comparing it to lab measurement. There were small difference, but we conclude that the difference is not major. However, the velocity of fresh rock differs significantly among samples: ranging from 3200 to 4400m/s. This cause a lot of error in CW estimation if we use typical fresh rock velocity as of 5000m/s. Thus accurate measurement of the velocity of fresh rock is crucial to CW estimation.