국내 고속도로의 본선차로 포장은 시공비용이 저렴한 줄눈 콘크리트 포장을 주로 시공하였으나, 최근 유지보수비용이 증가함에 따 라 유지관리비용이 저렴하고 공용성이 뛰어난 연속철근 콘크리트 포장을 확대 적용하고 있는 추세이다. 그러나 본선차로가 연속철근 콘크리트 포장으로 시공될 때 접속차로의 포장은 대부분 줄눈 콘크리트 포장으로 시공하고 있어 서로 다른 포장 형식이 접속함으로 인해 거동 차이가 발생하여 접속부에서 파손이 발생하기도 한다. 따라서 본 연구에서는 본선차로 연속철근 콘크리트 포장과 접속차로 줄눈 콘크리트 포장을 시공할 경우 줄눈 간격에 따른 접속차로 줄눈 콘크리트 포장의 응력 특성을 분석하기 위하여 유한요소해석 프 로그램을 이용하여 구조해석을 수행하였다. 줄눈 간격별로 줄눈 콘크리트 포장의 해석모델을 구성하였으며 환경하중인 선형수직온도 경사와 온도하강, 그리고 선형수직온도경사와 온도하강을 동시에 적용하여 해석을 실시하였다. 구조해석 결과, 모든 온도조건에서 줄 눈 간격이 좁아질수록 슬래브와 타이바의 응력이 감소하는 것으로 나타났다.

블로우업이 발생하는 구간에 ASR이 발생하고 있지만, 한국도로공사는 재료팽창인 ASR을 고려하지 않고, 콘크리트 팽창량을 계산하 여 팽창줄눈 설치간격을 제시하고 있다. 또한, 블로우업은 일종의 좌굴현상이므로 슬래브 두께에 따라 팽창줄눈 간격을 제시할 필요가 있다. 따라서 본연구는 재료팽창과 슬래브 두께를 고려하여 팽창줄눈 간격을 제시하고자 한다. 팽창량 계산시, 재료변형률과 지역별 온도와 건조수축을 고려하였으며, 이를 동등한 팽창을 유발하는 온도상승량으로 변환하는 식을 도출하였다. 기준온도를 정하기 위해 실제 현장데이터를 팽창량 식에 대입하여 온도상승량으로 변환하였으며, 이를 블로우업을 모사한 콘크리트 포장 모형의 유한요소해석 결과를 이용하여 결과값을 비교하였다. 안전설계를 위해 더 작은 온도 값인 블로우업 구조해석 결과 값 중 안전온도를 블로우업이 일 나는 기준으로 선정하였으며, 안전 온도를 넘지 않은 지역별 슬래브 두께에 따른 최대 팽창줄눈 간격을 제시했다. 한국도로공사가 제 시하고 있는 기준과 비교한 결과, 일부 지역은 한국도로공사에서 제시하고 있는 기준에 만족하지 않았다. ASR 변형률을 고려하여 슬 래브 두께에 따라 지역별로 팽창줄눈 간격을 제시하는 것이 블로우업 파손을 저감하고, 포장의 안정성을 향상시키는데 도움이 될 것 이라고 판단된다.

This experiment was conducted to investigate the change in the productivity of Italian ryegrass seeds according to the inter-row spacing in the southern region of the Korean Peninsula. Italian ryegrass (Lolium multiflorum Lam.) ‘Green Call’ variety was sown in Jinju, Gyeongnam in the fall of 2020 with three inter-row spacings (20, 30 and 40 cm). The experiment was arranged a randomized block design with three replications. The ryegrass was sown on October 17, 2020, and the harvest was on May 31, about 60 days from the first heading stage. There was no difference among treatments with an average of April 27th in heading stage. Plant height was significantly longer at 30 cm seeding interval and the shortest in 20 cm treatment. The length of the spike was the longest in the 40 cm seeding interval, and the number of seeds per spike was the highest in the 20cm seeding interval, but there was no significant difference among treatments. The seed yield was the highest at the 20 cm sowing interval (2,180 kg/ha), and decreased as the spacing increased. The dry matter content of seeds and straw was found to be 44.90% and 45.51% on average, and there was no significant difference among treatments. The amount of remaining straw after harvesting was found to be 7,506 kg/ha on average on DM basis, and was high at the 20 cm seeding interval. In view of the above results, it was found that it is most advantageous to sow at intervals of 20 cm when producing Italian ryegrass seeds through autumn sowing in the southern region.

To decrease area of the repository for high-level radioactive waste, enhancing the disposal efficiency is needed for public acceptance. Previous studies regarding the performance assessment of KRS and KRS+ repository did not consider area-based variations of the geothermal gradient and rock thermal properties in Korea. This research estimated deposition hole spacing based on performance assessment of a repository using the distribution of geothermal gradient and rock thermal properties in Korea to increase disposal efficiency. Distributions of geothermal gradient, rock thermal properties were investigated based on 2019 Korea geothermal atlas published by Korea Institute of Geoscience and Mineral Resources (KIGAM). Effect of thermal performance parameters was analyzed using coupled thermal-hydraulic numerical simulations, and effect of rock thermal conductivity and deposition hole spacing on the maximum temperature of buffer was relatively large. In addition, distribution maps of thermal performance of a repository and deposition hole spacing were plotted using thermal performance parameters-maximum temperature of buffer regression equations and GIS data given by KIGAM. In the regions showing the highest maximum temperature of buffer in Korea, required deposition hole spacings were 10.5 m, 10.0 m, 10.1 m, respectively for KJ-II, MX-80, and FEBEX bentonite cases, and thereby additional disposal area of 40%, 33.3%, and 34.7% were required compared to that of the KRS+ repository. On the other hand, high disposal efficiency can be obtained in the regions showing the low maximum temperature of bentonite buffer. The methodology provided in this research can be used as one of the references for the selection of domestic candidate repository sites. Additional mechanical performance analysis should be conducted using distributions of mechanical properties of rock mass in Korea.

해양데이터를 수집하기 위해 필요한 엔지니어, 연구원 및 과학자를 대신할 수 있는 해양 모니터링 장치인 자율주행보트의 필요성이 대두되고 있다. 이 논문은 자율주행보트의 세일을 개발하기 위한 연구로 곡선형 트윈 세일의 공기역학적인 특성을 수치해석적으로 분석하고 이를 날개 형태의 세일과 성능비교를 통해 곡선형 트윈 세일의 공기 역학적인 성능을 확인하였고, 세일의 간격과 형상에 따른 성능을 비교하였다. 유체 해석을 위한 지배방정식은 Navier - Stokes를 사용하였다. 성능비교 결과 곡선형 트윈 세일은 날개 형태의 세일과 비교하여 양력, 항력 및 추력 계수가 향상됨을 알 수 있다. 또한, 트윈 세일의 양 날개의 간격은 중요한 변수임을 확인 하였다. 0.035 L, 0.07 L, 0.14 L에서는 스톨로 인해 양력 계수의 감소로 나타났고 0.21 L, 0.28 L, 0.35 L에서는 개선되어 0.28 L에서 최대 양력을 보여 준다.

본 연구는 천연기념물로 지정하여 보호하고 있는 큰고니의 국내 최대 월동지인 낙동강하구일대 중 낙동강하류부를 대상으로 교량구간별 큰고니 월동개체의 서식처 선호도 차이를 살펴보고자 진행하였다. 2018~2019년 월동기 동안 6개 시계열로 구분하여 조사를 진행하여 분석한 결과 낙동강하류에서 최대 500여 마리의 큰고니가 월동하고 있었다. 하천을 가로지르는 교량을 기준으로 총 7개 구간을 설정하여 조사한 결과 큰고니는 교량과 교량사이가 2㎞ 이내로 협소한 5개 구간에서는 거의 관찰되지 않았고 4㎞이상의 2개 구간에서만 안정적 개체군이 관찰되었다. 이러한 특징은 인위적 간섭이 상대적으로 적어 큰고니의 주 서식지가 되고 있는 낙동강 하구로부터의 거리와는 관련이 없었다. 멸종위기종인 큰고니 월동에 있어 안정적 경계공간 확보는 중요한 요소로 판단되었다. 이에 멸종위기종인 큰고니 서식을 위해서는 교량과 교량 사이가 최소 4㎞ 이상 이격되어야만 하는 것으로 나타났다. 이러한 결과는 향후 교량건설과 같은 하천생태계의 단절로 직결되는 개발 또는 복원에 있어 하나의 참고가 될 것이다.

This paper discusses the influence of transverse reinforcement spacing and support width of concrete wide beam on shear performance. In order to evaluate the shear performance, a total of thirteen specimens were constructed and tested. The transverse reinforcement spacing, the number of legs and support width were considered as variables. From the test results, the shear strength equation of concrete wide beam is proposed for prediction of shear strength of concrete wide beam to consider the transverse reinforcement spacing and support width. It is shown that the proposed equation is able to predict shear strength reasonably well for concrete wide beam.

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.

PURPOSES : In this study, the propriety of expansion joint spacing of airport concrete pavement was examined by using weather and material characteristics. METHODS: A finite element model for simulating airport concrete pavement was developed and blowup occurrence due to temperature increase was analyzed. The critical temperature causing the expansion of concrete slab and blow up at the expansion joint was calculated according to the initial vertical displacement at the joint. The amount of expansion that can occur in the concrete slab for 20 years of design life was calculated by summing the expansion and contraction by temperature, alkali-silica reaction, and drying shrinkage. The effective expansion of pavement section between adjacent expansion joints was calculated by subtracting the effective width of expansion joint from the summation of the expansion of the pavement section. The temperature change causing the effective expansion of pavement section was also calculated. The effective expansion equivalent temperature change was compared to the critical temperature, which causes the blowup, according to expansion joint spacing to verify the propriety of expansion joint applied to the airport concrete pavement. RESULTS: When an initial vertical displacement of the expansion joint was 3mm or less, the blowup never occurred for 300m of joint spacing which is used in Korean airports currently. But, there was a risk of blow-up when an initial vertical displacement of the expansion joint was 5mm or more due to the weather or material characteristics. CONCLUSIONS: It was confirmed that the intial vertical displacement at the expansion joint could be managed below 3mm from the previous research results. Accordingly it was concluded that the 300m of current expansion joint spacing of Korean airports could be used without blowup by controling the alkali-silica reaction below its allowable limit.

A number of roller-compacted concrete pavements (RCCP) have been constructed without saw-cut joints in order to save construction cost. Then it will allow natural cracks to randomly occur at the early age after concrete placement. Crack spacing of unjointed RCCP is crucial to ensure an adequate crack width and load transfer across the cracks since large crack spacing will result in excessive crack width and reduce load transfer efficiency that may be cause faulting, excessive deflection, and further cracking in RCCP slab. Due to pavement thickness, climatic condition, and material properties, unjointed RCCP may have different natural crack spacing. In this study, an analytical approach to predict natural crack spacing of an unjointed RCCP was developed. An analytical method based on elastic theory to calculate axial restraint stress using a bilinear slab-subbase interfacial constraint assumption was conducted. Curling stress induced by temperature gradient through the depth of the slab was also considered. The analytical model incorporates the environmental effect, strength gain and modulus of elasticity, coefficient of thermal expansion, drying shrinkage, base type materials, and slab geometries. The predicted crack spacing results obtained from the predictive model were validated through field measured data. The results showed a good agreement compared with crack spacing measured in the field. Furthermore, the result from a sensitive analysis using proposed predictive model showed that crack spacing increased when thickness of RCCP increased. The predicted crack spacing results may be used as input parameters to estimate crack widths in unjointed RCCP under given climatic condition, and material properties. If estimated crack width is excessive and cannot maintain an adequate load transfer across the cracks, saw-cut joints with an appropriate spacing should be provided in order to minimize crack width, and to prevent future cracking of RCCP leading to better performance.