Dynamic Limit and Predatory Pricing Under Uncertainty (불확실성하(不確實性下)의 동태적(動態的) 진입제한(進入制限) 및 약탈가격(掠奪價格) 책정(策定))
-
- KDI Journal of Economic Policy
- /
- v.13 no.1
- /
- pp.151-166
- /
- 1991
In this paper, a simple game-theoretic entry deterrence model is developed that integrates both limit pricing and predatory pricing. While there have been extensive studies which have dealt with predation and limit pricing separately, no study so far has analyzed these closely related practices in a unified framework. Treating each practice as if it were an independent phenomenon is, of course, an analytical necessity to abstract from complex realities. However, welfare analysis based on such a model may give misleading policy implications. By analyzing limit and predatory pricing within a single framework, this paper attempts to shed some light on the effects of interactions between these two frequently cited tactics of entry deterrence. Another distinctive feature of the paper is that limit and predatory pricing emerge, in equilibrium, as rational, profit maximizing strategies in the model. Until recently, the only conclusion from formal analyses of predatory pricing was that predation is unlikely to take place if every economic agent is assumed to be rational. This conclusion rests upon the argument that predation is costly; that is, it inflicts more losses upon the predator than upon the rival producer, and, therefore, is unlikely to succeed in driving out the rival, who understands that the price cutting, if it ever takes place, must be temporary. Recently several attempts have been made to overcome this modelling difficulty by Kreps and Wilson, Milgram and Roberts, Benoit, Fudenberg and Tirole, and Roberts. With the exception of Roberts, however, these studies, though successful in preserving the rationality of players, still share one serious weakness in that they resort to ad hoc, external constraints in order to generate profit maximizing predation. The present paper uses a highly stylized model of Cournot duopoly and derives the equilibrium predatory strategy without invoking external constraints except the assumption of asymmetrically distributed information. The underlying intuition behind the model can be summarized as follows. Imagine a firm that is considering entry into a monopolist's market but is uncertain about the incumbent firm's cost structure. If the monopolist has low cost, the rival would rather not enter because it would be difficult to compete with an efficient, low-cost firm. If the monopolist has high costs, however, the rival will definitely enter the market because it can make positive profits. In this situation, if the incumbent firm unwittingly produces its monopoly output, the entrant can infer the nature of the monopolist's cost by observing the monopolist's price. Knowing this, the high cost monopolist increases its output level up to what would have been produced by a low cost firm in an effort to conceal its cost condition. This constitutes limit pricing. The same logic applies when there is a rival competitor in the market. Producing a high cost duopoly output is self-revealing and thus to be avoided. Therefore, the firm chooses to produce the low cost duopoly output, consequently inflicting losses to the entrant or rival producer, thus acting in a predatory manner. The policy implications of the analysis are rather mixed. Contrary to the widely accepted hypothesis that predation is, at best, a negative sum game, and thus, a strategy that is unlikely to be played from the outset, this paper concludes that predation can be real occurence by showing that it can arise as an effective profit maximizing strategy. This conclusion alone may imply that the government can play a role in increasing the consumer welfare, say, by banning predation or limit pricing. However, the problem is that it is rather difficult to ascribe any welfare losses to these kinds of entry deterring practices. This difficulty arises from the fact that if the same practices have been adopted by a low cost firm, they could not be called entry-deterring. Moreover, the high cost incumbent in the model is doing exactly what the low cost firm would have done to keep the market to itself. All in all, this paper suggests that a government injunction of limit and predatory pricing should be applied with great care, evaluating each case on its own basis. Hasty generalization may work to the detriment, rather than the enhancement of consumer welfare.
Recently, increase of demand for big data analysis has been driving the vigorous development of related technologies and tools. In addition, development of IT and increased penetration rate of smart devices are producing a large amount of data. According to this phenomenon, data analysis technology is rapidly becoming popular. Also, attempts to acquire insights through data analysis have been continuously increasing. It means that the big data analysis will be more important in various industries for the foreseeable future. Big data analysis is generally performed by a small number of experts and delivered to each demander of analysis. However, increase of interest about big data analysis arouses activation of computer programming education and development of many programs for data analysis. Accordingly, the entry barriers of big data analysis are gradually lowering and data analysis technology being spread out. As the result, big data analysis is expected to be performed by demanders of analysis themselves. Along with this, interest about various unstructured data is continually increasing. Especially, a lot of attention is focused on using text data. Emergence of new platforms and techniques using the web bring about mass production of text data and active attempt to analyze text data. Furthermore, result of text analysis has been utilized in various fields. Text mining is a concept that embraces various theories and techniques for text analysis. Many text mining techniques are utilized in this field for various research purposes, topic modeling is one of the most widely used and studied. Topic modeling is a technique that extracts the major issues from a lot of documents, identifies the documents that correspond to each issue and provides identified documents as a cluster. It is evaluated as a very useful technique in that reflect the semantic elements of the document. Traditional topic modeling is based on the distribution of key terms across the entire document. Thus, it is essential to analyze the entire document at once to identify topic of each document. This condition causes a long time in analysis process when topic modeling is applied to a lot of documents. In addition, it has a scalability problem that is an exponential increase in the processing time with the increase of analysis objects. This problem is particularly noticeable when the documents are distributed across multiple systems or regions. To overcome these problems, divide and conquer approach can be applied to topic modeling. It means dividing a large number of documents into sub-units and deriving topics through repetition of topic modeling to each unit. This method can be used for topic modeling on a large number of documents with limited system resources, and can improve processing speed of topic modeling. It also can significantly reduce analysis time and cost through ability to analyze documents in each location or place without combining analysis object documents. However, despite many advantages, this method has two major problems. First, the relationship between local topics derived from each unit and global topics derived from entire document is unclear. It means that in each document, local topics can be identified, but global topics cannot be identified. Second, a method for measuring the accuracy of the proposed methodology should be established. That is to say, assuming that global topic is ideal answer, the difference in a local topic on a global topic needs to be measured. By those difficulties, the study in this method is not performed sufficiently, compare with other studies dealing with topic modeling. In this paper, we propose a topic modeling approach to solve the above two problems. First of all, we divide the entire document cluster(Global set) into sub-clusters(Local set), and generate the reduced entire document cluster(RGS, Reduced global set) that consist of delegated documents extracted from each local set. We try to solve the first problem by mapping RGS topics and local topics. Along with this, we verify the accuracy of the proposed methodology by detecting documents, whether to be discerned as the same topic at result of global and local set. Using 24,000 news articles, we conduct experiments to evaluate practical applicability of the proposed methodology. In addition, through additional experiment, we confirmed that the proposed methodology can provide similar results to the entire topic modeling. We also proposed a reasonable method for comparing the result of both methods.
A university is an organization charged with publicity and has accountability to the community for the operating process. Students account for a majority of members in a university. In universities, numerous creatures are pouring out every year and university students are major producers of these records. However, roles and functions of university students producing enormous amount of records as main agents of universities and focused concentration on produced records have not been made yet. It is reality that from the archival point of view, the importance of produced records of which main agents are university students has been relatively underestimated. In this background, this study attempted approach in archival point of view on records produced by university students, main agents. There are various types of records that university students produce such as records produced in the process of research and teaching as well as records produced in the process of various autonomy activities like clubs, students' associations. This study especially focused on university student autonomy activity process and placed emphasis on accountability securing measures on autonomy activity process of university students. To secure accountability of activities, records management should be based. Therefore, as a way to ensure accountability of unversity students autonomy activity, we tried to present records management systematization and records utilization measures. For this, a student body, a university student autonomy organization was analyzed and a student body of Myongji University Humanities Campus was selected as a specific target. First, to identify records management status, activities and organization and functions of the student body, we conducted an interview with the president of the student body. Through this, we analyzed the activities of the university student body and examined the necessity of accountability accordingly. Also, we derived the types and characteristics of records to be produced at each stage by analyzing the organization and functions of the student body of Myongji University. Like this, after deriving the types of production records according to the necessity, organization and functions of accountability and activities of the student body, we analyzed records management status of the present student body. First, to identify the general process status of activities of the student body, we analyzed activity process by stage of the student body of Myongji University. And we analyzed records management method of the student body and responsibility principal and conducted real condition analysis. Through this analysis, we presented the measures to ensure accountability of a university student body in three categories such as systematization of records management process, establishment of records management infrastructure, accountability guarantee measures. This study discussed accountability on society by analyzing activities and functions of a student body, targeting a student body, an autonomy organization of university students. And as a measure to secure accountability of a student body, we proposed a model for records management environment settlement. But in terms that a student body is an organization operated in one year basis, there is a limit that records management environment is hard to settle. This study pointed out this limit and was to provide clues when more active researches were carried out in the field of student records management in the future through presentation of student body records management model. Also, it is expected that the analysis results derived from this research will have significance in terms of school history arrangement and conservation.
Kimura's Disease is a chronic inflammatory and proliferative condition producing subcutaneous masses especially in the head and neck area. This report of our experience with 5 patients with this disease is the first in the Korean surgical literature. Kimura's Disease is thought to be part of the larger spectrum of the entity known as angiolymphoid hyperplasia with eosinophilia (ALHE). It is characterized pathologically by hyperplastic lymphoid follicles, eosinophilic infiltration, and vase 비 ar proliferation. It produces masses which are most common in the area of the parotid, submandibular gland and upper neck. These masses occupy the subcutaneous tissues but also extend into salivary tissue and into upper neck nodes. One of our patients had masses in the groin. The tumors are extremely vascular due to the presence of new proliferative vessels and sinusoids. The average age of our 5 patients was 35, but all but one case were younger than 38 years of age. The male: female ratio was 3 : 2, and the average duration of symptoms was 5,2years. All patients had peripheral blood eosinophilia. All had multiple masses, sometimes symmetrical. The management was surgery alone in one case, surgery and steroids in one case, surgery and radiotherapy in two cases, and all three modalities in one case. The relationship of this entity to ALHE and our experience in the management of this disease are presented. A clinicopathological discrepancy alerted us to the existence of Kimura's Disease. A nineteen-year old male presented with subcutaneous masses over both mastoid areas present for 3 years (Case III). When biopsy on each side was reported as 'eosinophilic granuloma' we submitted the slides to an internationally expert pathologist. Symmetrically occurring tumors in the peri-parotid subcutaneous areas did not fit any category of neoplasm or granuloma known to us. The diagnosis, made by Dr. Gist Fan at the Ochsner Clinic, was Kimura's Disease. We found two additional cases in a review of soft tissue eosinophilic granuloma previously reported at Presbyterian Medical Center, and since then have diagnosed two new cases. These five cases constitute the basis for this, the largest series to be reported in Korea. These vascular, tumor-like lesions of the skin, subcutaneous areas and subjacent structures of the head and neck have been a variety of names, such as angiolymphoid hyperplasia with eosinophilia, eosinophilic hyperplastic lymphogranuloma, angioblastic lymphoid hyperplasia with eosinophilia, histioid hemangioma, and epithelioid hemangioma. The history of this disease spectrum dates back to 1937 when Kimm and Szeto (1) reported 7 cases of 'eosinophilic hyperplastic lymphogranuloma' in the Proceedings of the Chinese Medical Journal. In 1948 Kimura and his associates(2) reported additional cases in Japan under the title 'On the unusual granulation combined with hyperplastic changes of lymphatic tissue.' From then until 1966 several hundred cases were reported in China and Japan. The first report from the West was by Wells and Whimster(3) in the British Journal of Dermatology, in 1969. These authors coined the term, angiolymphoid hyperplasia with eosinophilia (ALHE). Since that time a debate has ensued as to whether Kimura's Disease and ALHE are distinct entities, or whether Kimura's is part of the larger spectrum of ALHE, perhaps a later or advanced phase. From the clinical perspective, surgeons should be aware of the diagnosis of Kimura's Disease not only as part of the differential diagnosis of head and neck tumors but also because these lesions are indolent, and generally require conservative surgical removal as part of the management program. CASE I. A 37-year-old female company employee presented in August 1982 with submental swelling of 12 years' duration and with inguinal swelling of 7 years' duration. The submental mass measured 5x5cm. and the inguinal mass was 8x4cm. in size. Peripheral eosinophilia varying from 14% to 40% was found. On August 20, 1982, the submental mass was removed and a superficial groin dissection was done. In May 1983 an intraoral lesion of the palate was removed. The patient is free of disease. CASE II. A 23-year-old unemployed man visited this hospital for the first time in July, 1984, with swelling of the right cheek present for 6 years. The mass was soft and ill-defined but measured 10x20cm. and extended from the submandibular upper neck to the zygomatic arch, and from the mastoid to the cheek, over the parotid gland. Eosinophilia varying from 27% to 29% was noted in the peripheral blood. On March 21, 1986, the lesion was resected. The procedure comprised an extended superficial parotidectomy from the temporalis fascia to the upper neck. Post-operatively radiotherapy 3000 rad tissue dose was administered using the 6 MeV linear accelerator. The patient remains free of disease. CASE III. A 19-year-old student came to the clinic with masses over both mastoid areas, present 3 years. On the right there were two adjacent lesions, one over the mastoid, the other in the upper jugular level of the neck. On the left it was a single mass over the mastoid. Eosinophilia varied from 13 to 32% in the peripheral blood, and 11.6% in the bone marrow. Incisional biopsy revealed 'eosinophilic granuloma' and a trial of predisolone was employed. The mass increased in size so a small dose of radiation (600 rads) was used, with substantial regression,. The lesion on the left was excised and follwed by 1000 rads radiotherapy. Finally recurrent tumor on the right side was removed on November 5, 1985. The patient remains free of disease. CASE N. A 29-year-old local merchant had had swelling of both upper necks since childhood. At the time of his first visit on March 17, 1986, the right submandibular mass measured 5x3.5cm. and the ,right upper neck and parotid tail mass measured 2.5cm. On the left there were masses in the upper neck, the largest of which measured 2.5cm, and of the parotid tail, 2.0cm. in size.(See Fig. 1) Peripheral eosinophilia of 39% was recorded. Left side partial parotidectomy and resection of the upper neck and subdigstric mases was done on May 2, 1986. The mass involving the right parotid tail and upper neck nodes was removed on Angust 7,1986. Postoperatively the patient was placed on prednisolone 30 mg. per day. No definite masses are palpable. CASE V. A 66-year-old housewife informed us, at the time of her first visit in May, 1986, that she had had multiple neck masses since 10 years ago. On the right side there was a 2.5cm. subcutaneous mass of the upper neck, over the upper jugular chain. On the left there was a 9x4.5cm. mass involving the entire parotid, the post-auricular area and the upper neck. A third mass presented in the submental area and measured 3.5cm. (See Fig. 2) Eosinophilia of 51% was noted in the peripheral blood. partial excision of the left upper neck lesion and complete excision of the submental mass were performed on june 6, 1986. post-operatively she was placed on 20 mg. of prednisolone daily, but when the mass re-grew after two months she was referred to Radiation Therapy for a 2500 rad course of treatment. A barely palpable thickening remains.
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