주파수 변화에 따른 에폭시 복합체의 전기적 특성을 알아보기 위하여 온도 범위 20[℃], 100[℃], 140[℃], 주파수 범위 30[Hz]~3[MHz] 사이에서 유전율 및 유전손실을 측정하였다. 저주파 영역에서 유전분산과 유전 손실이 나타나고 있음을 확인하였다. 또한 고온 영역에서는 충진제의 영향으로 유전율이 감소하는 것을 확인하였다.

The purposes of this study are to analyze high-frequency hedges in dissertations and provide basic data for Korean education for academic purposes. For these purposes, the investigator analyzed ‘-(으)ㄹ 수 있 다, -(으)ㄹ 것이다, and -(으)로 보이다’ in terms of frequency, distribution by the structure, and forms of combination in 50 dissertations for a master’s degree. The findings were as follows: first, ‘-(으)ㄹ 수 있다, -(으)ㄹ 것이다, and -(으)로 보이다’ were used total 3,880 times across all the dissertations. Of them, ‘-(으)ㄹ 수 있다’ were used 2,496 times, recording an overwhelmingly higher frequency than the others. Secondly, the study analyzed the frequency of hedges by the part in dissertations and found that hedges were most used in “Findings”(56.6%). Finally, there were standardized forms frequently combined with each hedge. ‘-(으)ㄹ 수 있다,’ for instance, was frequently used in the forms of ‘-(이)라고 할 수 있다/다고 할 수 있다,’ ‘-(으)ㅁ을 알 수 있다,’ and ‘-다는 것을 알 수 있다.’

Large space structures exhibit different natural vibration characteristics depending on the aspect ratio of structures such as half-open angle. In addition, since the actual large space structure is mostly supported by the lower structure, it is expected that the natural vibration characteristics of the upper structure and the entire structure will vary depending on the lower structure. Therefore, in this study, the natural vibration characteristics of the dome structure are analyzed according to the natural frequency ratio by controlling the stiffness of the substructure. As the natural frequency of the substructure increases, the natural frequency of the whole structure increases similarly to the natural frequency of the upper structure. Vertical vibration modes dominate at 30° and 45°, and horizontal vibration modes dominate at 60° and 90°.

Background: At present time, smartphones have become very popular and powerful devices, and smartphone applications with the good validity have been designed to assess human balance ability. Objects: The purpose of this study is to evaluate the feasibility of smartphone acceleration in the assessment of postural control ability for six different conditions. Methods: Twenty healthy college-aged individuals volunteered. Static balance ability was measured twice with one-day interval using smartphone application and 3D motion capture system under the six different conditions. Results: Dominant frequencies for each test condition did not show significant differences except for two conditions. The intra-rater correlation coefficient between the first and second tests showed high correlations in six conditions(r>.70, p<.05). Smartphone acceleration and the acceleration calculated from the 3D marker position data showed high correlation coefficient(r>.80, p<.001). Conclusion: Acceleration recorded from a smartphone could be useful assessment variables for balance test in the clinical field.

High power trends in the diesel engines due to engine downsizing do not provide noise attenuation that can be satisfied with the performance of the existing silencer on account of high frequency increases in the exhaust noise. This study improves the attenuation performance of the exhaust silencer of the diesel engine and suggests silencer structure that performs best attenuation performance, especially at the high frequency range in the exhaust noise. It proposes dual silencer structure with an average attenuation performance of 6.4 dB and a maximum of 10.7 dB in the high frequency range (over 500 Hz), and analyzes its characteristics compared with the existing silencer. The performance analysis is performed according to 'Measurements on silencers in situation–ISO 11820:1996 Acoustics' and describes the results of comparative analysis with the existing silencer.

Introduction Social media marketing is an attractive marketing method for fostering relationships with customers. About 30% of social media users find social networking sites important when searching for information about brands as well as showing their support towards them (Nielsen, 2017). This engagement with brands on social media is one of the factors driving company outcomes. For example, consumer engagement in social media brand communities is found to have a positive impact on purchase spending (Goh, Heng, and Lin, 2013), brand equity (Christodoulides and Jevons, 2012), and brand attitude (Schivinski and Dabrowski 2016). Consumer engagement involves both consumer interaction and co-creation of the content (Smith and Gallicano, 2015). In order to enhance engagement with brand content, marketers must persuade consumers to interact with those messages by sharing, commenting or liking them (Chang, Yu, Lu, 2014). Hence, interaction is the crucial step towards improving consumer engagement. While marketers rely on experimenting in order to find elements that drive consumer interaction, researchers use vast social media data in order to examine relationships between brand message characteristics and consumer interaction with those messages. For example, (Vries, Gensler, and Leeflang, 2012) studied the impact of post’s vividness, interactivity, content, position of a post and valence of comments on brand post popularity as represented by number of likes and comments. Other researchers such as (Wang et al ,2016) examined the impact of topic, tone and the length of post on social media engagement defined not only by the number of likes and shares, but also by the likability of characters featured in the post. Chang, Yu, and Lu (2014) studied how argument quality, post popularity, and post attractiveness can lead to consumer engagement. Similarly, (Lee and Hong, 2016) investigated the impact of emotional appeal, informativeness and creativity of a message on positive consumer behavior towards brand message. However, little is known so far about the effects of the frequency and spacing of brand-generated content on the dynamics of consumer interaction. Advertising research shows that advertising frequency has an impact on various consumer behavior and attitude outcomes and suggests that there is an optimum level of exposure to advertising that yields greatest results (Schmidt and Eisend, 2015; Broussard, 2000). Moreover, research on advertising repetition in traditional channels suggests an inverted u-shape relationship between ad repetition and message effectiveness. This happens because at a certain number of exposures negative factors, such as boredom and irritation (Heflin and Haygood, 1985), kick in and overweigh positive ones. As a result, the effectiveness of an ad starts diminishing. This effect is also known as the wear-out effect. On the other hand, (Lee, Ahn, and Park, 2015) suggest that inverted U-shape relationship between repetition and attitude towards the brand does not hold true in online environments. This is the case because users can control their exposure to advertising, therefore they do not expose themselves to the ad to the extent that they feel adverse toward it. As firm-generated brand content on social media is a form of advertising, it is interesting to examine, whether wear-out effect occurs in the context of social media and user interaction. In addition, the effect of advertising repetition is found to depend on the time period, or space, between ad exposures (Janiszewski, Noel, and Saywer, 2003). Spacing between exposures affect learning (Sawyer, Noel, and Janiszewski, 2009), attitude towards the brand (Schmidt and Eisend, 2015), purchase spending (Sahni, 2015), attrition rate and customer response (Dreze and Bonfrer, 2008). Moreover, recent study by (Wang, Greenwood, and Pavlou, 2017), who investigated the influence of posting on the propensity to unfollow the brand on the largest social media in China WeChat, found that posting leads to higher likelihood of unfollowing the brand, which in turn has a negative effect on the long term sales. However, WeChat may be considered to be more intrusive than Facebook because of the differences in how followers get notified about new brand posts. Therefore, it is interesting to examine whether the same effect of posting holds true on Facebook. Finally, viral marketing research suggests that the growth rate of interaction with the content depends on the rate of creation of other messages (Karnik, Saroop, and Borkar, 2013). Based on the findings from previous studies, it is evident that frequency and spacing may have a significant influence on the level and growth rate of user interaction. Furthermore, two-sided advertising research suggests that inclusion of negative information in product related messages can yield better results in terms of persuasive power than if no negative information is included (Eisend 2006). In addition, political communication researchers found that sentiment-carrying Twitter messages tend to be retweeted more often and more quickly (Stieglitz and Dang-Xuan, 2013). Therefore, it is suggested that the effect of message frequency and spacing on the level of consumer interaction is moderated by the sentiment of the message. In other words, the optimal level of message frequency is expected to be higher for emotionally-charged firm-generated brand messages as compared to neutral ones. Hence, the following research questions are proposed: RQ1: How does frequency and spacing of brand-generated content affect the dynamics of consumer interaction on social media and how is this effect moderated by the sentiment of the content? RQ2: How does posting on social media affect the unfollowing by brand followers? RQ2a: Does the spacing between messages help reduce the negative effect of posting on the unfollowing by brand followers (if such effect is present)? Research Design & Theoretical Development In order to answer these questions two data sets were gathered via Facebook’s API consisting of 6,471 and 932 brand posts respectively. Two separate data sets were needed to examine the frequency effects on the overall level of consumer interaction as well as on the growth rate of interaction. Therefore, post and page data for 7 international brands from 5 different product categories for the period of 2 years were collected to examine the frequency effects. To investigate the effect of posting on the growth rate of consumer interaction, 11 brands were tracked for the 7-week period in order to capture the development of the interaction. In addition, the impact of posting on the propensity to unfollow the brand was examined. Consequently, three separate regression models were built to test the hypotheses. Results showed that frequency of posting and the level of consumer interaction has an inverted u-shape relationship and that the level of consumer interaction is positively influenced by the space between the posts. Further, findings suggest that posting on social media is positively associated with unfollowing by followers and that the growth rate of interaction of the post depends on the rate of new message generation by the same brand. The conceptual model is presented below. Result and Conclusion The study has few theoretical and practical contributions. Answering to the call for research (Vries, Gensler, and Leeflang, 2012) to include the dynamic aspects of interaction, this study contributes to the social media literature by examining the effects of the rate of new message generation on the growth rate of interaction of the post. In addition, this study adds to the stream of research on the wear-out effects in online environments by including higher number of exposures and by testing the type of firm communication (social media communication) that previously has not been studied. Finally, this study contributed to the recent research (Wang, Greenwood, and Pavlou, 2017) by examining the effect of posting on the unfollowing by brand followers. As for practical contributions, findings of this study have implications for marketing managers with respect to the frequency and spacing of posting. This study provides evidence for a more moderate posting strategies in terms of frequency.

The main purpose of this research is to explore the effects of usage frequency on the intention to reuse membership service while having perceived value play a role as a mediator. Usage frequency of membership services can affect consumers' fairness judgment. The more opportunities consumers have to perceive the fairness of a service, the more likely it is that they will choose to receive the identical service from the same provider in the future, since they form a positive attitude toward the service. In addition, the perceived value of the consumer can lead to the reuse of the service because it gives satisfaction to the consumer. Another objective of this research is to examine the moderating effect of regret and guilt on the relationship between perceived value and the intention to reuse membership service. Consistent with regret literature, if consumers perceive a consumption value that is smaller than the initially expected consumption value when using a membership service, they will regret the use of the service. Further, negative emotion such as regret often lead to negative attitudes and behaviors of consumers. Thus, as consumers feel regret, their willingness to use the membership service will continue to decrease. On the other hand, consumers experience guilt when they benefit from an unfair process (Krehbiel and Cropanzano, 2000). Similarly, when consumers judge that they have exceeded the usage frequency of membership service based on social norms or ethical principles of individuals, they will perceive unfairness. Consumers may try to offset their negative emotion by continuing to use identical membership services even after the end of the contract period as compensation for their guilty feelings. Thus, as consumers feel guilt, their willingness to use the membership service will continue to increase. This study proposes practical implications that a firm operating a membership service program can encourage a positive response of consumers in their service process by theoretically identifying the intrinsic process related to consumers' intention to reuse the service.

위험유해물질은 해양에 유입되었을 때 인간의 건강 및 해양생태계에 막대한 영향을 미치는 물질로 정의된다. 최근 선박을 이용한 물동량이 증가되면서 위험유해물질 누출사고의 발생비율도 증가되는 추세이다. 이에 따라 위험유해물질 누출사고 대응기술개발의 관점에서 해저에 침적되는 물질들의 방제 및 모니터링 연구가 수행되어야 한다. 본 논문에서는 저층 침적 위험유해물질의 음향 탐지 가능성을 확인하기 위해 저층 침적 위험유해물질 대체물질의 반사손실 측정 실험이 수행되었다. 위험유해물질로 구분되는 클로로폼의 위험성을 고려하여 클로로폼과 임피던스가 유사한 피마자유가 대체물질로 사용되었으며, 200 kHz 고주파 신호를 송신하여 물과 피마자유 경 계면에서 발생되는 반사손실을 측정하였다. 그리고 물과 피마자유의 임피던스를 측정 및 조사하여 반사계수를 모의하고 모의된 반사손실이 측정값과 유사함을 확인하였다. 또한 저층 침적 위험유해물질로 분류되는 클로로폼의 반사손실을 모의하고 모의 결과가 다양한 해저면 구성성분의 반사손실 모의결과와 차이를 나타냄으로써 해저면과 구분되는 저층 침적 위험유해물질의 음향 탐지 가능성을 예측하였다.

Pavement performance usually depends on the pavement’s material property, traffic and environmental conditions. Current pavement design programs such as the Mechanistic Empirical Pavement Design Guide use these factors in assessing the pavement life and performance in terms of different distresses like rutting and fatigue cracking. Theoretically, the cracking and rutting behaviour of pavements are based on accumulated strains experienced by the pavement which is brought by the weight and loading speed of vehicles. A steady state loading device was used in the field to evaluate pavement deflection’s behaviour in varying loading frequencies. It was observed that the pavement deflection increases as the loading frequency also increases until it approaches a certain frequency wherein the deflection decreases thereafter. In this study, a three-dimensional finite element pavement model was established using ABAQUS wherein the effect of the vehicle’s loading frequencies was analysed. The calculated static deflection and stress from the finite element (FE) model were found to have good correlation with the KENPAVE measured deflection and stress. The deflections of different pavement conditions were further studied and analysed by generating several pavement geometries and strength from the FE model using a frequency sweep response analysis. It was found that the geometric condition and the current modulus of the pavement can amplify the pavement deflection by a factor, β, depending on the loading frequency. The peak deflection was found to be occurring when the loading frequency approaches one of the pavement’s natural frequencies. Based on the finding from this study, the natural frequency is an important factor to be considered in designing pavements. Further study is recommended to understand more on how to minimize the effect of natural frequency to pavement life.

향후 통일 이후 북한 지역의 급격한 국토 개발로 인한 자연 환경 훼손을 미연에 방지하기 위해 식생지수와 토지피복지도 등 원격탐사 기법을 이용한 평가 항목과 빈도비 분석을 이용하여 환경생태적 우수 지역 평가를 수행했다. 빈도비를 이용한 환경생태적 우수 지역 확률 지도의 ROC 분석 결과 87.1%의 높은 정확도가 나타났다. 그리고 빈도비를 이용한 환경생태적 우수 지역 결과와 국토환경성평가지도와의 Kappa를 이용한 비교 분석에서 높은 적합성을 나타냈다. 이에 빈도비를 이용한 환경생태적 우수 지역 평가 기법을 이용한 환경생태적 우수 지역 평가 결과는 향후 통일을 대비한 각종 개발 및 환경 보전 계획을 수립에 도움이 될 수 있으며, 더 나아가 한반도의 지속 가능한 국토 관리에 큰 기여할 수 있을 것으로 기대된다.

Following the earthquake that shook the city of Gyeongju, Korea, in 2016, it became apparent that research on the safety of cultural heritages against the seismic hazards is necessary in Korea. Predictions of how historically significant stone pagodas would behave the earthquakes anticipated in near future, which are the subject of this study, is also required. In this study, the dynamic characteristics of 15 cultural heritage designated stone pagodas of Korea were investigated, including natural frequency and damping ratio, and the stiffness of the stone material and its contact area were determined using eigenvalue analysis by assuming the stone pagodas to be multi-degree-of-freedom structures. The results of this study enable the structural modeling of stone pagodas using a finite element analysis program and the method is expected to be useful in assessing the structural safety of stone pagodas against vertical loads as well as lateral forces, including earthquakes. Also, by identifying the dynamic characteristics of the structures, the results of this study can be utilized as a nondestructive testing method to determine the rigidity of cultural heritage structures and to identify inherent problems. The natural frequencies of the Korean stone pagodas were measured to be within 3.5~8.3㎐, excluding cases with distinct natural frequency results, and it was determined that the natural frequencies of the stone pagodas are influenced by various parameters including the height and joint stiffness of the structures.

Theories for composite structures are too difficult for design engineers for construction. The purpose of this paper is to demonstrate to the practicing engineers, how to apply the advanced composite materials theory to the structures. In this study, the natural frequency of a laminated cantilever beam was studied. An ultrasonic testing platform was employed to resonate the beam, and its time domain signal was optically measured. The natural frequency was quantified through the fast Fourier transform of the waveform, and the result showed good agreement with a theoretical estimation from the Euler-Bernoulli beam theory. This study is expected to provide a dynamic evaluation technique for laminated cantilever beam structures.

오늘날까지 적층 마이크로 외팔보의 고유진동수에 대하여 연구가 진행되었다. 마이크로 보는 실리콘 재질로 만들어 지지만, 그것의 상하 표면은 얇은 금 박막층(~30nm)이 증착되어 있다. 초음파 검사를 위해 초음파 테스트 플랫폼을 사용했으며, 시간영역 신호는 광학적으로 측정되었다. 고유진동수는 파형을 고속 Fourier 변환을 통해 정량화하였으며, 결과적으로 고전적인 보 이론과 일치하는 결과를 보여 주었다. 본 연구는 마이크로/나노스케일 재료와 마이크로 구조에 대한 동적평가기법 을 제공할 것으로 기대된다.

Pseudo-static approach has been conventionally applied for the design of gravity type quay walls. In this method, seismic coefficient (kh), expressed in terms of acceleration due to gravity, is used to convert the real dynamic behavior to an equivalent pseudo-static inertial force for seismic analysis and design. Therefore, the calculation of an appropriate kh considering frequency characteristics of input earthquake is critical for representing the real dynamic behavior. However, the definitions of kh, which is used for simplified analysis in Korea, focuses only on convenience that is easy to use, and the frequency characteristics of input earthquake are not reflected in the kh definitions. This paper evaluates the influences of the frequency characteristics of input earthquake on kh by initially reviewing the kh definitions in the existing codes of Japan for port structures and then by performing a series of dynamic centrifuge tests on caisson gravity quay walls of different earthquake input motions (Ofunato, Hachinohe). A review of the existing codes and guidelines has shown that the kh values are differently estimated according to the frequency characteristics of input earthquake. On the other hand, based on the centrifuge tests, it was found that the permanent displacements of wall are more induced when long-period-dominant earthquake is applied.

We measured the target strength according to the swimming tilt angle and size change for Pacific herring at the frequency of 70 kHz as the basic database in order to estimate its abundance as well as density in the survey area using the hydroacoustical method. The number of the sample used in this study was 14 individuals, and its size distribution by fork length ranged between 20.3 and 29.8 cm and wet weight was measured between 187.6 and 269.9 g. The variation of TS according to the swimming angle (-30~30°) was measured between 10.3 and 18.8 dB in frequency range, the highest value was measured at head-down of Pacific herring in the tilt angle range between 5 and 9 deg. of its swimbladder. The relationship between TS–FL of herring was the same as TS = 20log10 (FL) – 66.79 when its swimming tilt angle in the daytime (3.8 ± 6.0°) and nighttime (-3.2 ± 13.6°), respectively.

We investigate the radio properties of the dwarf galaxy SDSS J133245.62+263449.3 which shows optical signatures of black hole activity. Dwarf galaxies are known to host intermediate mass black holes (IMBHs) with masses MBH ∼ 10 4-6 M⊙, some of them being radio loud. Recently, Reines et al. (2013) found dwarf galaxy candidates which show signatures of being black hole hosts based on optical spectral lines. SDSS J133245.62+263449.3 is one of them; it shows a flux density of ∼ 20 mJy at 1.4 GHz, which corresponds to L 1.4GHz ∼ 10 23 WHz -1. This is much brighter than other black hole host dwarf galaxies. However, star formation activity can contribute to radio continuum emission as well. To understand the nature of the radio emission from SDSS J133245.62 + 263449.3, we imaged this radio loud dwarf galaxy at low frequencies (325 MHz and 610 MHz) using the Giant Metrewave Radio Telescope (GMRT). We present here the high resolution images from our GMRT observations. While we detect no obvious extended emission from radio jets from the central AGN, we do find the emission to be moderately extended and unlikely to be dominated by disk star formation. VLBI observations using the Korean VLBI Network (KVN) are now being planned to understand the emission morphology and radiation mechanism.