The benefit that a consumer derives from the use of a good often depends on the number of other consumers purchasing the same goods or other compatible items. This property, which is known as network externality, is significant in many IT related industries. Over the past few decades, network externalities have been recognized in the context of physical networks such as the telephone and railroad industries. Today, as many products are provided as a form of system that consists of compatible components, the appreciation of network externality is becoming increasingly important. Network externalities have been extensively studied among economists who have been seeking to explain new phenomena resulting from rapid advancements in ICT (Information and Communication Technology). As a result of these efforts, a new body of theories for 'New Economy' has been proposed. The theoretical bottom-line argument of such theories is that technologies subject to network effects exhibit multiple equilibriums and will finally lock into a monopoly with one standard cornering the entire market. They emphasize that such "tippiness" is a typical characteristic in such networked markets, describing that multiple incompatible technologies rarely coexist and that the switch to a single, leading standard occurs suddenly. Moreover, it is argued that this standardization process is path dependent, and the ultimate outcome is unpredictable. With incomplete information about other actors' preferences, there can be excess inertia, as consumers only moderately favor the change, and hence are themselves insufficiently motivated to start the bandwagon rolling, but would get on it once it did start to roll. This startup problem can prevent the adoption of any standard at all, even if it is preferred by everyone. Conversely, excess momentum is another possible outcome, for example, if a sponsoring firm uses low prices during early periods of diffusion. The aim of this paper is to analyze the dynamics of the adoption process in markets exhibiting network effects by focusing on two factors; switching and agent heterogeneity. Switching is an important factor that should be considered in analyzing the adoption process. An agent's switching invokes switching by other adopters, which brings about a positive feedback process that can significantly complicate the adoption process. Agent heterogeneity also plays a important role in shaping the early development of the adoption process, which has a significant impact on the later development of the process. The effects of these two factors are analyzed by developing an agent-based simulation model. ABM is a computer-based simulation methodology that can offer many advantages over traditional analytical approaches. The model is designed such that agents have diverse preferences regarding technology and are allowed to switch their previous choice. The simulation results showed that the adoption processes in a market exhibiting networks effects are significantly affected by the distribution of agents and the occurrence of switching. In particular, it is found that both weak heterogeneity and strong network effects cause agents to start to switch early and this plays a role of expediting the emergence of 'lock-in.' When network effects are strong, agents are easily affected by changes in early market shares. This causes agents to switch earlier and in turn speeds up the market's tipping. The same effect is found in the case of highly homogeneous agents. When agents are highly homogeneous, the market starts to tip toward one technology rapidly, and its choice is not always consistent with the populations' initial inclination. Increased volatility and faster lock-in increase the possibility that the market will reach an unexpected outcome. The primary contribution of this study is the elucidation of the role of parameters characterizing the market in the development of the lock-in process, and identification of conditions where such unexpected outcomes happen.
The relevance of this scientific research is determined by the negative impact of the COVID-19 pandemic on the current trends and dynamics of world tourism development. This article aims to identify patterns of development of the modern tourist market, analysis of problems and prospects of development in the context of the COVID-19 pandemic. Materials and methods. General scientific methods and methods of research are used in the work: analysis, synthesis, comparison, analysis of statistical data. The analysis of the viewpoints of foreign and domestic authors on the research of the international tourist market allowed us to substantiate the actual directions of tourism development due to the influence of negative factors connected with the spread of a new coronavirus infection COVID-19. Economic-statistical, abstract-logical, and economic-mathematical methods of research were used during the process of study and data processing. Results. The analysis of the current state of the tourist market by world regions was carried out. It was found that tourism is one of the most affected sectors from COVID-19, as, by the end of 2020, the total number of tourist arrivals in the world decreased by 74% compared to the same period in 2019. The consequence of this decline was a loss of total global tourism revenues by the end of 2020, which equaled $1.3 trillion. 27% of all destinations are completely closed to international tourism. At the end of 2020, the economy of international tourism has shrunk by about 80%. In 2020 the world traveled 98 million fewer people (-83%) relative to the same period last year. Tourism was hit hardest by the pandemic in the Asia-Pacific region, where travel restrictions are as strict as possible. International arrivals in this region fell by 84% (300 million). The Middle East and Africa recorded declines of 75 and 70 percent. Despite a small and short-lived recovery in the summer of 2020, Europe lost 71% of the tourist flow, with the European continent recording the largest drop in absolute terms compared with 2019, 500 million. In North and South America, foreign arrivals declined. It is revealed that a significant decrease in tourist flows leads to a massive loss of jobs, a sharp decline in foreign exchange earnings and taxes, which limits the ability of states to support the tourism industry. Three possible scenarios of exit of the tourist industry from the crisis, reflecting the most probable changes of monthly tourist flows, are considered. The characteristics of respondents from Ukraine, Germany, and the USA and their attitude to travel depending on gender, age, education level, professional status, and monthly income are presented. About 57% of respondents from Ukraine, Poland, and the United States were planning a tourist trip in 2021. Note that people with higher or secondary education were more willing to plan such a trip. The results of the empirical study confirm that interest in domestic tourism has increased significantly in 2021. The regression model of dependence of the number of domestic tourist trips on the example of Ukraine with time tendency (t) and seasonal variations (Turˆt = 7288,498 - 20,58t - 410,88∑5) it forecast for 2020, which allows stabilizing the process of tourist trips after the pandemic to use this model to forecast for any country. Discussion. We should emphasize the seriousness of the COVID-19 pandemic and the fact that many experts and scientists believe in the long-term recovery of the tourism industry. In our opinion, the governments of the countries need to refocus on domestic tourism and deal with infrastructure development, search for new niches, formats, formation of new package deals in new - domestic - segment (new products' development (tourist routes, exhibitions, sightseeing programs, special rehabilitation programs after COVID) -19 in sanatoriums, etc.); creation of individual offers for different target audiences). Conclusions. Thus, the identified trends are associated with a decrease in the number of tourist flows, the negative impact of the pandemic on employment and income from tourism activities. International tourism needs two to four years before it returns to the level of 2019.
북한의 황폐산림 양상을 살펴보면 시기별 북한 내 정치 사회 경제적인 여건과 밀접한 관계를 맺으면서 변화해 왔음을 알 수 있다. 일반주민들에 의한 생존형 산림훼손은 1990년대 사회주의권의 붕괴와 수년에 걸친 자연재해로 인해 경제난이 심각해지고 중앙집권적 계획경제 체제가 붕괴되면서 가속화되었다. 계획경제 체제에서의 배급제가 붕괴되면서 주민들은 식량을 확보하기 위한 수단으로 산지를 무분별하게 개간하였고, 땔감을 확보하기 위해 나무를 남벌하였다. 국가 기관들도 외화를 획득하기 위해 수출용 목재 벌채량을 늘리면서 북한 산림은 빠른 속도로 황폐화 되었다. 산림황폐화로 인한 피해가 확대되면서 북한은 결국 산림복구를 위한 자구책을 마련하는 한편 국제사회에 산림복구 지원을 요청하였다. 이에 남한 민간단체도 조림용 묘목생산의 기반인 양묘장 건설을 위주로 하는 물적 지원 사업을 시작하였다. 그러나 앞으로의 북한 산림복구 지원은 현재와 같은 단순한 물적 지원을 벗어나 1970년대 남한의 치산녹화 성공 경험을 토대로 다음과 같은 북한의 경제사회적 여건을 고려한 황폐산림복구 기본방향을 설정하고 체계적으로 추진하는 것이 필요하다. 첫째, 2000년 이후 북한의 중앙집권적 계획경제 체제가 붕괴된 이후 조성되고 있는 지방, 기업, 노동자간 다양한 이해관계를 고려한 산림복구지원이 이루어져야 한다. 두 번째, 장기간 주민들의 적극적인 참여가 요구되는 산림복구 사업의 특성상 산림복구 현장에서 경제적 이익을 얻을 수 있도록 하여 주민들의 자발적인 참여도를 높이도록 해야 한다. 세 번째, 산림복구 사업과 병행하여 농산촌 종합개발 사업을 연계하여 주민들의 산림의존도를 낮춰가는 것이 필요하다. 네 번째, 기존의 북한 산림관리 시스템을 활용하여 단기간 대규모 집중 조림에 필요한 노동력과 행정력을 확보하는 한편, 산림복구 이후의 산림관리를 체계적으로 담당할 수 있는 시스템의 개선도 함께 진행되어야 한다.
이 글의 목적은 대순진리회의 생태주의 담론인 '상생생태론'에서 '상생'의 의미를 생태적으로 규정하는 데 있다. 인간을 대상으로 윤리적 측면에서 통용되던 상생이 그 적용 범위를 비인간까지 확장시키는 생태학의 영역에서 어떻게 적용될 수 있는지 상호의존성이라는 생태학의 개념으로 설명한다. 생태학에서의 상호의존성은 개체와 개체 사이에서 발생하는 긍정적, 부정적, 중립적인 관계를 조합하여 경쟁, 포식, 기생, 그리고 공생으로 구분한다. 개체와 개체 사이의 관계가 부정적으로 끝나더라도 생태계에는 긍정적인 영향을 끼칠 수 있으므로 모두 '의존'이라는 개념에 포함된다. 그러나 개체와 개체 사이의 부정적 결말은 원을 발생시킬 수 있고 이러한 상호의존은 상생윤리의 관점에서는 그대로 통용될 수 없다. 따라서 생태적 상생은 긍정적 상호의존의 관계만 해당하거나 혹은 포원이 존재하지 않는 포식, 기생, 경쟁의 관계도 포함될 수 있다. 생태론은 자연과 인간을 분리하지 않고 둘 사이를 통합적으로 이해할 수 있는 관점을 요구한다. 천지생인용인(天地生人用人)이라는 우주관은 우주와 인간, 자연과 인간의 관계를 상호의존적 관점에서 포착할 수 있게 한다. 천지는 자신의 존재 근거를 인간으로 삼았고, 지인은 자연의 법칙을 발견하고 그 배후에 있는 천지의 신성성까지 깨달아 비로소 천지와 인간, 자연과 인간의 깊은 상호의존의 관계가 성립한다. 그러나 근대적 인간이 등장하면서 자연을 짓밟고 신도의 권위를 떨어뜨림으로써 천지와 인간의 상호의존성은 붕괴된다. 해원상생과 보은상생은 천지와 인간, 자연과 인간 사이에 끊어진 상호의존성을 다시잇는 해결책이다. 공부 의례를 통해 해원상생을 실천하는 것은 자연과 인간의 상호의존성을 회복하는 길이다. 수도를 통해 도통에 도달하는 과정이 보은상생의 실천이며 이로써 인간은 생태적 본성을 지닌 인존으로 거듭나 자연과 영원한 상호의존을 누리게 된다. 요컨대 상생생태론에서의 상생은 자연과 인간이 상호의존성을 회복하고 그것을 영원히 지속할 수 있게 만드는 이념이자 실천이다.
자기폭풍(magnetic storm)과 서브스톰(substorm)의 인과관계를 규명하기 위하여 서브스톰 확장기 활동(substorm expansive activity)의 전형적인 지시자로 알려진 정지궤도 위성에서 관측된 양성자 플럭스(proton flux)의 무분산 입자유입률(dispersionless particle injection rate)과 Dst 지수와의 상관관계를 조사하였다. 본 연구에 이용된 자기폭풍은 1996년에서 2000년까지 5년 동안에 일어난 것으로 자기폭풍 기간 중 Dst의 최소값인
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70
The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70