Businesses today are looking for new ways to acquire and retain customers, by delivering innovative products and services, which serve each customer's individual demands. Fo- cusing on individual customer needs and addressing each request individually with a ser- vice or product that is perceived as being customized has become the focal point of Inter- action Orientation (IO), a firm-level strategic orientation developed by Ramani and Kumar (2008). Entrepreneurial Orientation (EO) is also a firm-level strategic construct, which reflects the "processes, practices, and decision-making activities" that firms use to identify and exploit new business opportunities (Lumpkin & Dess, 1996, p.136). As op- posed to IO, EO is a well-established concept, being one of the most examined topics in entrepreneurship research. However, most studies have focused on cross-sectional de- signs to assess the relationship to firm performance, leading to numerous research calls focusing on the need for more dynamic investigations (Saeed, Yousafzai, & Engelen, 2014). Based on our analysis including 247 S&P500 firms from a variety of industries over a period of three years, this longitudinal study is one of the first to assess the short-term and long-term effects of IO and EO. To establish the firm's levels of IO and EO, we ana- lyze the content of Letters to Shareholders (LtS), as LtS have been widely used to assess different strategic orientations - Market Orientation, Learning Orientation - including EO (Noble et al., 2002; Short, Broberg, Cogliser, & Brigham, 2010; Zachary, McKenny, Short, & Payne, 2011). We relied on multisource secondary data for performance indica- tors and included several control variables: past performance of the firm, firm age, firm size, as well as industry specific effects. Our results confirm that each orientation has a positive impact on the firm's financial suc- cess in the long-term but a combined IO-EO strategy reveals a negative effect on firm performance in the long-term. This study investigates the synergies between IO and EO in a longitudinal setting and using objective financial performance indicators, establish- ing the advantages and disadvantages of implementing a single or combined strategy.

Interaction Orientation (IO), a firm-level strategic orientation developed by Ramani and Kumar (2008), consists of four dimensions: (1) Customer concept - a firm-wide belief that sees the individual customer level as the examination unit and starting point of all company’s activities; (2) Interaction response capacity - the firm’s competency to respond to different customers using multiple means in a timely manner; (3) Customer empowerment - the extent to which a firm encourages customers to share information with the firm or with other customers; and (4) Customer value management - the capacity to keep an overview of how much revenue each customer generates, facilitating an efficient resource allocation. Current research states that IO represents a source of competitive advantage and leads to higher financial and non-financial performance. Past studies have only focused on cross-sectional data. However, a strategic orientation is a deeply embedded and gradually progressing organizational characteristic and, in order to establish a cause-effect relationship with performance, a longitudinal design is needed (Noble, Sinha, & Kumar, 2002). This study is the first to analyze the effects of IO longitudinally, including 247 S&P 500 firms from a variety of industries over a period of three years. To establish the firm's level of IO, we analyze the content of Letters to Shareholders (LtS). LtS are widely used to assess different strategic orientations, such as Entrepreneurial Orientation, Market Orientation or Learning Orientation (Noble et al., 2002; Short, Broberg, Cogliser, & Brigham, 2010; Zachary, McKenny, Short, & Payne, 2011). A sentence-by-sentence coding procedure was implemented (Keusch, Bollen, & Hassink, 2012;), where each sentence was examined for evidence of the four IO dimensions. We relied on multisource secondary data for performance indicators and on the American Customer Satisfaction Index (ASCI) for measuring customer satisfaction. We included the effects of competitive intensity and market turbulence, as well as several control variables: past performance of the firm, firm age, firm size, as well as industry specific effects. The results confirm the short and long term benefits of implementing IO, including higher financial performance and increased customer satisfaction, especially in a turbulent market. This study lays the foundation of a new approach for measuring IO in a longitudinal setting and using objective financial performance indicators.

The purpose of this study was to explore how motivational factors affect Korean EFL secondary students’ motivated learning behavior using structural equation modeling (SEM). It further examined differences in the internal structure of L2 motivation over time. A total of 489 secondary school students participated in the study. Data were collected at two time points during an academic semester: in the beginning and at the end of the semester. Results of the SEM showed that students’ ideal L2 self was the strongest determinant of their motivated learning behavior at both time points for middle school students, whereas for high school students, ought-to L2 self had the strongest direct and significant impact on their motivated behavior in learning English throughout the semester. It was also found that both middle and high school students’ perceptions about the international posture of English and their parents’ involvement in English learning made indirect effects on their motivated behavior. Pedagogical implications and research suggestions are discussed.

This paper presents aspects of eight advanced Korean EFL speakers' acquisition of English unaccusative verbs over a period of five years. It examines how three factors−L1 morphology, pragmatic causation, and animacy−have affected their English unaccusative verb grammar during that time. A forced-elicitation grammaticality judgment task was performed three times over this period. It showed that L1 morphology was the most persistent among these factors. The results are compared with Chung (2014), a cross-sectional study, where the same method was used. The findings reveal that the Korean EFL subjects' overpassivization of English unaccusatives is not fossilized, which differs from the findings of Han (2006), who examined two Chinese native learners of English. It also indicates that instruction can play an important role in long-term L2 learning.

PURPOSES : This study aims to evaluate the road safety of the super-elevation transition section of a left turn curve and suggest the minimum longitudinal grade of a super-elevation transition section to be used before and after a left curved section. METHODS: We evaluated the road condition by means of the safety-criterion-evaluation method involving side friction factors, and then solve the problem by introducing the minimum longitudinal grade criterion based on conditions described in the hydraulics literature. RESULTS : It was calculated that when a road satisfies hydroplaning conditions, the difference between side friction assumed and side friction demanded is less than - 0.04. In this case, the safety criterion for the condition is unsatisfied. Conversely, when a road is in a normal state under either wet or dry conditions, it was calculated that the difference between side friction assumed and side friction demanded is more than 0.01. Thus, the safety criterion for this condition is found to be satisfied. After adjusting the minimum longitudinal grade applied to a super-elevation transition section, the hydroplaning condition can be eliminated and the safety criterion can be met for all sections. CONCLUSIONS : It is suggested that a minimum longitudinal grade should be provided on super-elevation transition sections in order to prevent hydroplaning.

본 연구에서는 2D 화면과 3D화면으로 각각 제시된 운전 시뮬레이션 환경에서 운전자의 종적 차량통제, 주관 적 피로감 및 지각된 현실감에서의 차이를 비교하였다. 본 연구의 결과들을 요약하면 다음과 같다. 첫째, 실험참 가자들은 미리 정해진 네 가지 수준의 목표속도(60, 80, 100 및 120km/h)를 유지할 때 3D 조건보다는 2D 조건에 서, 그리고 목표속도가 낮을수록 목표속도에 비해 더 빠르게 운전하였고, 이러한 경향은 목표속도 조건과 상관없 이 일정하였다. 둘째, 선행차량과의 차간거리 유지수행에 대한 분석 결과, 2D 조건에 비해 3D 조건에서 실험참가 자들은 선행차량과 더 근접한 차간거리를 유지하며 주행하였는데, 특히 선행차량의 주행속도가 비교적 느렸던 조건(즉, 60km/h)에 비해 비교적 빨랐던 조건(즉, 80 및 100km/h)에서 이러한 경향이 두드러졌다. 셋째, 속도 유지 과제와 선행차량과의 차간거리 유지수행 모두에서 2D 조건에 비해 3D 조건에서 실험참가자들이 경험하는 피로 감의 수준이 더 높았으나 주관적 현실감에 대한 평가에서는 두 가지 과제 모두에서 2D와 3D 조건에 따라 유의 한 차이가 관찰되지 않았다.

PURPOSES: The purpose of this study is to evaluate the degree of restraint (DOR) of longitudinal steel at continuously reinforced concrete pavement (CRCP) against environmental loadings. METHODS : To measure the longitudinal steel strain, 3-electrical resistance and self-temperature compensation gauges were installed to CRCP test section (thickness = 250mm, steel ratio = 0.7%) and continuously measured 10 min. intervals during 259 days. In order to properly analyze the steel strains first, temperature compensation process has been conducted. Secondly, measured steel strains were divided into 12 phases with different events such as before paving, during concrete hardening, and after first cracking, etc. RESULTS : Thermal strain rate (TSR) concept is defined as the linear strain variations with temperature changes and restraints rate of longitudinal steel against environmental loadings (especially thermal loading) with different cases is defined as degree of restraint(DOR). New concept of DOR could be indirect indicator of crack width behaviors of CRCP. CONCLUSIONS: Before paving, DOR of longitudinal steel is almost same at the coefficient of thermal expansion of steel (12.44m/m/℃) because of no restraint boundary condition. After concrete pouring, DOR is gradually changed into -1 due to concrete stiffness developing with hydration. After first cracking at crack induced area, values of DOR are around -3~-5. The negative DOR stands for the crack width behavior instead of steel strain behavior. During winter season, DOR reached to -5.77 as the highest, but spring this values gradually reduced as -1.7 as the lowest. Based on this observation, we can presume crack width decreased over time within the time frame of this study. This finding is not consistent with the current theory on crack width variations over time, so further study is necessary to identify the causes of crack width reducing. One of the reasons could be related to concrete stress re-distribution and stress relaxation.

PURPOSES : The purpose of this study is to analyse the longitudinal steel strain and stress of continuously reinforced concrete pavement(CRCP) with longitudinal and transverse direction at early age using stress dependent strain analysis method. METHODS : To measure the longitudinal steel strain, 9-electrical resistance and self-temperature compensation gauges were installed to CRCP test section (thickness = 250mm, steel ratio = 0.7%) and continuously measured 10min. intervals during 30days. In order to properly analyze the steel stress first, temperature compensation process has been conducted. Secondly, measured steel strains were divided into stress dependent strain (elastic strain) and stress independent strain (thermal strain) and then stress dependent strain was applied to stress calculation of longitudinal steels. RESULTS: Steel strains were successfully measured during 30days. To verify the accuracy of temperature compensation process, measured coefficient of thermal expansion(COTE,11.46×10-6m/m/℃) of longitudinal steel before paving was compared with that of unrestrained steel. Max. steel stress in the transverse direction shows about 266MPa at 23days after placement. CONCLUSIONS: Steel stresses in the longitudinal and transverse direction have been evaluated. In longitudinal direction, steel stress from the crack was rapidly reduced from 183MPa at crack to 18MPa from 600mm apart the crack. From this observation, stress effective length can be identified as within 600mm apart from the crack. In transverse direction, max. stress point was located near the center of pavement width and stress level(266MPa) is about 66% of yield stress of steel

본 연구에서는 수중익 배치와 종모멘트 특성이 전몰형 수중익선의 종방향 운동 안정성에 미치는 영향에 대하여 Tandem 수중익 모형의 시험을 통하여 고찰한다. 먼저, Canard 날개배치를 가지는 Tandem 수중익 모형을 제작하고 수중익의 양력 및 항력 계측 실험을 수행하여 양력 및 항력 특성을 평가하였다. 또한 종방향 운동의 초기 안정성과 자기 안정성을 가지는 Tandem 수중익 모형의 날개 배치를 결정하였다. Tandem 수중익 모형의 종안정성 시험에서는 선수 및 선미 수중익의 종방향 간격 변화와 종모멘트의 자기안정성 변화에 따른 Pitch 및 Heave 운동 특성, 익주 상태의 종안정성을 평가하였다. 먼저, Canard 날개배치를 가지는 Tandem 수중익 모형을 제작하고 수중익의 양력 및 항력 계측실험을 수행하여 양력 및 항력 특성을 평가하였다. 또한 종방향 운동의 초기 안정성과 자기 안정성을 가지는 Tandem 수중익 모형의 날개 배치를 결정하였다. Tandem 수중익 모형의 종안정성 시험에서는 선수 및 선미 수중익의 종방향 간격 변화와 종모멘트의 자기안정성 변화에 따른 Pitch 및 Heave 운동 특성, 익주 상태의 종안정성을 평가하였다. 실험 수행 결과 본 연구의 주요 결론의 다음과 같다. 종 모멘트 자기 안정성이 클수록 주어진 고정 pitch 각에서 pitch운동에 대한 자기안정성이 높다. 다음 종모멘트 자기 안정성이 클수록, pitch각도 변화에 따른 pitch운동 및 heave운동의 변동 폭이 상대적으로 작으며 종방향 안정성이 우수하다. 마지막으로 종모멘트 자기안정성이 클수록, 수중익 양력이 동일한 경우, Tandem 수중익의 안정적인 익주를 위해서는 충분한 종모멘트의 자기안정성을 확보하는 것이 필수적인 것을 시험을 통하여 확인하였다.

As advances in digital technologies (e.g., Apps, QR code, RFID tag) is rapidly changing market environment, marketing researches have extended technology acceptance models in different contexts. Since a supermarket chain, “Home Plus,” in Korea, had opened the first QR code virtual store at the subway platform in 2011, many firms attempt to use QR code technology convergence into their retail business. According to a survey report (Embrian, 2012), QR codes are highly familiar with consumers in Korea, and more than 70% mobile phone users have ever scanned QR codes. Due to ubiquitous nature of QR codes, it is obviously implied that marketers would capitalize the QR code technology on their retail business. Yet, it is skeptical for individuals to adopt QR code virtual store because it is in an infant stage in the retail store context. Therefore, marketers need to predict acceptance and use of QR code virtual store from a consumer perspective. Based on UTAUT (Unified Theory of Acceptance and Use of Technology) suggested by Venkatesh et al. (2003; 2012), this study formulated consumer acceptance model with four core determinants of intentions in the context of QR code virtual stores. Specific objectives are (a) identify perceived value in the context of QR code virtual store; (b) test the changes in consumer perceived value by experience over time; and (c) to predict UTAUT model for consumer acceptance to use QR code virtual store across different time points (i.e., from the time of their initial introduction to stages of experience). A longitudinal field study was conducted at the selected QR code virtual stores among individuals using smart phones. A self-administered questionnaire was developed based on literatures the context of consumer use of QR code virtual store. The multi-item scales of perceived value (i.e., performance expectancy, effort expectance, social influence, and facilitating condition) were adapted from Venkatesh et al.’s (2003) UTAUT constructs. Four items of behavioral intention to use QR code virtual store was developed. All items were measured on 5 points rating scale. Sample in this study was obtained from volunteers who participated in three different points in time: initial experience (T1), one month after first experience (T2) and three months after second experience (T3). Participants were required to visit to an assigned QR code store and do shopping task per each time. Then, they were asked to answer the questions on a survey, and there were 123 valid respondents to the first stage of the field experiment. As removed the respondents who did not participate in T2 or T3 point, a total of 309 pooled data across time (103 each time) were analyzed. The sample represents more females (n=66, 68%) than males (n=31, 32%), aging from 19 to 29 years (mean=21.58 years). Preliminarily, using the data pooled across times, factor analysis was conducted to identify underlying constructs for all research variables. As expected, a factor analysis of perceived value constructs revealed four factors: social influence (5 items), performance expectancy (5 items), effort expectancy (4 items), and facilitating condition (3 items). All factor loadings were ranged from .63 to .86, and all internal consistency reliabilities were greater than .80. Also, a unidimensional behavioral intention (4 items) confirmed to be valid (factor loadings=.88 to .93) and reliable (α=.94). Therefore, it is deemed that content validity and reliability were within acceptable ranges for further analysis. Of the four perceived value constructs, there were significant differences in the effort expectancy (F=7.10, p<.01) and facilitating condition (F=8.22, p<.001) across times of experience. Specifically, the perceive effort expectancy tended to be increased over time, indicating a difference of means between T1 and T2 at the significant level of .01 as a result of Duncan’s post-hoc test. With respect to facilitating condition, the mean tended to be increased over time, but post hoc test indicated a significant difference between T1 and T2. The perceived effort expectancy and facilitating condition tended to be changed in positive from T2 to T3 point, which were not significantly different. Therefore, the finding implies that the second stage of experience (i.e., one month after first experience) is a critical point for consumers to increase perceived value of QR code virtual store as a new retail technology. Otherwise, the other factors, such as social influence, performance expectancy and behavioral intention were not significantly increased during the three times of experience. To predict UTAUT model for consumer acceptance to use QR code virtual store, behavioral intention was served as dependent variable and the four factors of perceived value were served as independent variables in regression analysis. In the initial experience (T1), behavioral intention was significantly predicted by social influence (β=.39, t=4.42, p<.001) and performance expectancy (β=.46, t=4.44, p<.001), which explained for 57% of total variance (F=32.08, p<.001, adjusted R²=.57). In the second experience (T2), behavioral intention was significantly predicted by three factors, such as social influence (β=.43, t=5.91, p<.001), performance expectancy (β=.35, t=4.10, p<.001) and facilitating condition (β=.15, t=2.32, p<.05), accounted for 68 % of total variance (F=52.35, p<.001, adjusted R²=.68). In the three month after second experience (T3), behavioral intention was significantly predicted by social experience (β=.36, t=3.33, p<.01) and performance expectancy (β=.33, t=3.33, p<.001), accounted for 52 % of total variance (F=27.65, p<.001, adjusted R²=.52). This study supports the UTAUT model for consumer acceptance of QR code virtual store over time from a theoretical perspective. It should be noted that social influence and performance expectancy appears to be a determinant of behavioral intention to use in most situations. The effect of facilitating condition on behavioral intention was only significant when experienced in second stage. In addition, future study needs to expend technology acceptance model of virtual store in conjunction with digital technological attributes across different product categories.

Economic fluctuation has a remarkable influence on firms and their performance (e.g., Deleersnyder, Dekimpe, Sarvavy, & Parker, 2004; Srinivasan, Rangaswamy, & Lilien, 2005). Given the extreme conditions and frequency of recessions (since World War II, recessions have occurred every six years; Srinivasan et al., 2005), understanding what kind of marketing is effective across the different phases of the economic cycle is a crucial question for marketers (e.g., Steenkamp & Fang, 2011; Srinivasan, Lilien, & Sridhar, 2011). In business-to-business markets, characterized by a strong emphasis on long-term customer relationships (e.g., Grönroos, 1997), the ability to gain a deep understanding of customers and their changing needs is a central determinant of firm performance. Therefore, in such markets, market orientation (MO) provides a particularly important source of competitive advantage. During an economic crisis, MO may also serve as an effective shelter against declining firm performance, particularly in industrial markets (Alajoutsijärvi, Klint, & Tikkanen, 2001). The key rationale is that highly market-oriented firms are able to rapidly and accurately identify changes in the marketplace and respond to shifting customer needs and competitors’ actions (Narver & Slater, 1990). While a vast body of literature evidences MO in general to yield performance gains for firms (Kirca, Jayachandran, & Bearden, 2005), some recent studies (e.g., Kumar, Jones, Venkatesan, & Leone, 2011) have questioned this relationship. Recent empirical studies (e.g., De Luca, Verona, & Vicari, 2010; Noble, Sinha, & Kumar, 2002) also propose that the different components of MO (i.e., customer orientation, competitor orientation and interfunctional coordination) may result in different performance outcomes. Furthermore, recent studies have shown the economic environment to play an important role in determining the performance outcomes and, thus, effective forms of MO (cf. Smirnova, Naudé, Henneberg, Mouzas, & Kouchtch, 2011). In this study, using panel data of 140 firms from before and after the great financial crisis, we examine the performance implications of distinct forms of MO 1) over the changing economic cycle 2) among different types of business-to-business focused firms. Employing ordinary least squares regression analysis, our findings suggest that MO and its distinct components yield varying performance impacts from economic upturn to downturn. Specifically, the impact of MO increases during downturn, with interfunctional coordination boosting performance and competitor orientation becoming detrimental. Subsequently, employing configurational analysis (fuzzy set qualitative comparative analysis), our findings further indicate that the role and the most effective forms of MO vary across industry sectors, with MO having a particularly strong impact among firms operating in business-to-business services. We also conclude that, in a growing economy the role of MO has become more of a cost of competing (Kumar et al., 2011), whereas in an economic downturn MO still provides a valuable shelter against performance declines. Finally, our empirical findings are in line with contingency arguments, and suggest that the successful ways for a firm to relate with its markets depend on the dynamic firm- and industry-specific settings.

The plastic hinge region of RC pier ensures its nonlinear behavior during strong earthquake events. It is assumed that the piers secure sufficient strength and ductility in order to prevent the collapse of the bridge during strong earthquake. However, the presence of a lap-splice of longitudinal bars in the plastic hinge region may lead to the occurrence of early bond failure in the lap-splice zone and result in significant loss of the seismic performance. The current regulations for seismic performance evaluation limit the ultimate strain and displacement ductility considering the eventual presence of lap-splice, but do not consider the lap-splice length. In this study, seismic performance test and analysis are performed according to the cross-sectional size and the lap-splice length in the case of longitudinal bars with lap-splice located in the plastic hinge region of existing RC bridge columns with circular cross-section. The seismic behavioral characteristics of the piers are also analyzed. Based upon the results, this paper presents a more reasonable seismic performance evaluation method considering the lap-splice length and the cross-sectional size of the column.

여객과 화물의 고속 해상수송을 위하여 다양한 형태의 고속선이 개발되고 있으며 특히 40노트 이상의 고속 운항에 적합한 전몰형 수중익선에 대한 연구가 요구되고 있다. 전몰형 수중익선은 익주 상태의 안정적인 운항을 위해서는 종방향 운동의 안정성 확보가 필수적이다. 본 연구에서는 수중익 배치와 종모멘트 특성이 전몰형 수중익선의 종방향 운동 안정성에 미치는 영향에 대하여 Tandem 수중익 모형의 시험을 통하여 고찰한다.

In head sea, a ship has mainly the longitudinal motion such as vertical acceleration and pitch. In that case, the motion characteristics of a ship will have changed as the location different from each of place vertically and horizontally on board. The author carried out an experiment about the ship's vertical acceleration and pitch according to the location for the head sea, and analyzed the data with the aid of the statistical and spectral analyzing method to get the motion characteristics of the vessels. The response of vertical acceleration and pitch not deeply depend on the decks vertically, but displayed the relative big different value horizontally even if same deck. The biggest response of vertical acceleration and pitch among the accommodations was shown at scientist room, but the value of it not reached to the minimum requirement of ISO 2631-1 for working on board.

본 연구에서는 실습선의 다방향 불규칙파중 종방향 운동응답특성을 선형 스트립이론에 기초한 상용코드(MAXSURF v.16)를 이용하여 해석하였다. 해석에 앞서 상용코드의 검증을 위해 파나막스급 컨테이너선에 대해 실험조건과 동일한 선형과 해석조건을 적용하여 계산한 결과와 기 계산된 결과(Flokstra, 1974)가 상호 유사한 경향을 얻어 해석의 신뢰성을 확보하였다. 계산조건으로는 Fn=0.257에서 파랑외력을 ITTC 파스펙트럼에 기초한 뷰포트 스케일 5(T=5.46, H1/3=2m)의 파스펙트럼을 산출하였고, 조우각은 선수사파(Head & bow seas, 150˚)를 적용하여 상하동요(Heave)와 종동요(Pitch)의 선체운동응답스펙트럼을 해석하였다. 다방향 불규칙파에 대한 운동응답스펙트럼은 선수사파에서 상하동요의 경우는 미소하게 단파정파에서 높은 스펙트럼 분포를 보이고 종동요의 경우는 장파정파에서 높게 나타났다.

목 적: 중학생(14~16세)과 고등학생(17~19세)의 굴절이상도를 2년간 추적하여 굴절이상의 변화를 분석, 비교하고 이의 결과를 중고생 근시 진행에 관한 자료와 근시 예방 대책을 세우는데 기본 자료로 제시하고자 한다. 방 법: 전북에 소재한 안경원에 첫 번째 검사(2009.01.01~2009.09.30), 12개월 후(두 번째 검사, 2010.01.01~2010.09.30), 24개월 후(세 번째 검사, 2011.01.01~2011.09.30)와 같이 12개월을 주기로 3회 이상 내원한 현재 중학생 3학년 150명, 현재 고등학생 3학년 150명의 동일대상의 굴절검사 기록을 비교, 분 석하였다. 굴절이상의 검사는 기존의 안경 굴절력을 바탕으로 타각적, 자각적 굴절검사를 시행하였다. 결 과: 첫 번째 검사, 12개월 후, 24개월 후 측정한 전체 평균 등가구면 굴절력은 중학생 -3.55D± 2.44D, 고등학생 -4.70D±2.18D이었다. 굴절이상의 평균 변화는 첫 번째 검사에서 24개월 후 중학생이 -0.90D±0.19D, 고등학생이 -0.85D±0.17D로 중학생에서 평균 변화량이 약간 높았다. 안경의 굴절력은 1 단계가 0.25D이므로 근시도의 -0.25D의 변화를 1단계(step)의 변화로 나타내었다. 근시 진행량은 1단계 이 하(-0.25D 이하), 2~3단계(-0.50D~-0.75D), 4단계 이상(-1.00D 이상)으로 나누었다. 중학생 첫 번째 검 사에서 24개월 후 근시 진행량은 1단계 이하 11.67%, 2~3단계 38.34%, 4단계 이상은 50.00%로 조사되었 다. 고등학생 첫 번째 검사에서 24개월 후 1단계 이하는 9.70%, 2~3단계 44.00%, 4단계 이상은 46.30%로 조사되었다. 굴절상태와 굴절정도에 따라 A그룹(+0.75D 이상), B그룹(-0.75D~-2.75D), C그룹 (-3.00D~-5.75D), D그룹(-6.00D 이상)으로 구분하였다. 그룹별 전체 평균굴절력은 A그룹 2.25D±1.22D, B그룹 -2.32D±0.67D, C그룹 -4.70D±0.85D, D그룹은 -7.58D±1.05D로 조사되었다. 전체 안경 착용자 중 근시의 비율 변화는 중학생에서 첫 번째 검사, 12개월 후, 24개월 후 96.67%로 변화가 없었고, 고등학생 은 첫 번째 검사와 12개월 후 98.67%로 변화가 없었고, 24개월 후 99.67%로 1% 증가하였다. 결 론: 굴절이상이 있는 중고등학생 300명을 2년간 추적하여 굴절력을 분석하고 비교해 본 결과 근시의 발생율이 과거보다 현저하게 진행하였다. 많은 학생들이 긴 시간의 학업과 52.16%의 인터넷 중독(잠재적 중 독 포함)으로 인한 컴퓨터의 장시간 사용과 2009년 도입된 스마트폰의 장시간 사용이 가성근시에서 진성근 시로의 변화에 큰 영향을 미쳤을 것으로 판단된다. 학생들의 근시 진행을 예방하기위해 근거리 사용시간을 줄이는 적절한 대책이 계속적으로 논의되어야 할 것으로 사료된다.

판처럼 거동함을 밝히고, 간단한 공식들을 개발하여 발표한 바 있다. 대부분의 교량이나 건물의 상판은 형상비가 큰 경우가 많은데, 이런 구조물의 평형방정식에 대한 종방항 모멘트항(Mx)의 영향은 매우 작아서, 더욱 간단한 해 석이 가능하다. 본 논문에는 이러한 문제들에 대한 연구결과를 제시하였다.