발사플랫폼의 운용성 확장을 위한 지면기울기 보상기법

정재욱,김룡,Chung, Jae-Wook,Kim, Yong 한국군사과학기술학회 2012 한국군사과학기술학회지 Vol.15 No.1

When missile is launched, a launcher needs to be leveled with accuracy to avoid the systems's instability. In general, a launcher is leveled by adjusting the stroke of leveling jacks; however, it is still challenge to control the leveling jacks fast and accurately. This paper thus proposed an innovative algorithm for compensating ground inclination of a missile launcher to expand operational field of a missile launcher. Using two inclinometers attached on a launcher, a base jack for leveling is selected and the mixed gradient where launcher stands on can be estimated. Due to the limited stroke, the launcher can compensate its ground inclination within maximum stroke margin. Then, the ground inclination of a launcher can be compensated by calculated angle using weighting factors. The effectiveness of proposed algorithm is proved with a prototype missile launcher.

파열식 발사관 덮개의 성능검증을 위한 시험기법

정재욱,신상목,배영관,Chung, Jae-Wook,Shin, Sang-Mok,Bae, Young-Gwan 한국군사과학기술학회 2013 한국군사과학기술학회지 Vol.16 No.4

When a missile is launched, a fracture-type canister cover should be properly broken by a collision with a missile or inner pressure of a canister. The fracture performance of a canister cover should be evaluated by a test using a real missile; however, it is unrealistic due to high cost and time restriction in a design stage. In this study, a test technique is newly developed to predict fracture performance of a canister cover. The test was design to have same kinetic energy with a real missile test when the cover is collide with a missile. The effectiveness of the suggested test technique was proved by comparing the test result with that of a real missile test.

하수준설토와 석분의 건설재료로 재활용을 위한 지반물성연구

정재욱,장연수,Chung, Jae-Wook,Jang, Yeon-Soo 한국지하수토양환경학회 2007 지하수토양환경 Vol.12 No.4

Geotechnical and environmental properties of stone fillers are analyzed by several laboratory experiment to identify the possibility of recycling fillers and sewage dredged soils as construction materials. The result of geotechnjical test shows that the sewage dredged soil is a sandy soil which contains 70-80% sand and is useful as an aggregate of construction site. Stone filler has large fine content, which may disqualifies the use as construction materials. However, this material is still useful as a filler in stone quarries or finished mines. From the environmental test, the liquids leached from two types of materials have satisfied the standard of chemical substances in the soil environment law and no harmful effect in ground pollution is expected when recycling. 본 연구에서는 석분과 하수준설토에 지반물성시험과 토양환경오염 우려기준에 의거한 오염도 측정을 실시하였다. 실험 결과 하수 준설토는 모래가 $70%{\sim}80%$의 비율의 사질계열의 흙으로써 건축 토목공사의 골재재료로써 가치가 크다는 것이 판명되었다. 석분은 세립분의 함량이 큰 관계로 건설재료로 좋은 품질을 보이지는 않았으나 폐광, 석산에서 석재 채취 후 빈 공간 등을 채우는 용도에 적용시킨다면 재활용이 가능한 것으로 나타났다. 유해물질 함유량은 두 시료 모두 토양오염우려기준에 훨씬 못 미치는 수치로서, 재활용시 토양오염에는 거의 영향이 없는 것으로 나타났다.

염산티트라싸이클린의 적용시간에 따른 다공성 임프란트 표면 미세구조의 변화

정재욱,허익,권영혁,박준봉,정종혁,Jeong, Jae-Wook,Herr, Yeek,Kwon, Young-Hyuk,Park, Joon-Bong,Chung, Jong-Hyuk 대한치주과학회 2006 Journal of Periodontal & Implant Science Vol.36 No.2

Mechanical and chemical methods are the two ways to treat the implant surfaces. By using mechanical method, it is difficult to eliminate bacteria and by-products from the rough implant surface and it can also cause the structural change to the implant surface. Therefore, chemical method is widely used in order to preserve and detoxicate the implant surface more effectively. The purpose of this study is to evaluate the effect of tetracylcline-hydrochloride(TC-HCI) on the change of implant surface microstructure according to application time. Implants with pure titanium machined surface, SLA surface and porous surface were used in this study. Implant surface was rubbed with sponge soaked in 50mg/ml TC-HCI solution for $\frac{1}{2}$ min., 1 min., $1\frac{1}{2}$ min., 2 min., and $2\frac{1}{2}$ min. respectively in the test group and with no treatment in the control group. Then, specimens were processed for scanning electron microscopic observation. 1. Both test and control group showed a few shallow grooves and ridges in pure titanium machined surface implants. There were not significant differences between two groups. 2. In the SLA surfaces, the control specimen showed that the macro roughness was achieved by large-grit sandblasting. Subsequently, the acid-etching process created the micro roughness, which thus was superimposed on the macro roughness. Irrespective of the application time of 50mg/ml TC-HCI solution, in general, test specimens were similar to control. 3. In the porous surfaces, the control specimen showed spherical particles of titanium alloy and its surface have a few shallow ridges. The roughness of surfaces conditioned with tetracycline-HCI was lessened and seen crater-like irregular surfaces relative to the application time. In conclusion, pure titanium machined surfaces and SLA surfaces weren't changed irrespective of the application time of tetracycline-HCI solution. But the porous surfaces conditioned with tetracycline-HCI solution began to be slightly changed from 2 min. This results are expected to be applied to the regenerative procedures for peri-implantitis treatment.

리더십 대체요인의 효과분석을 위한 모형설정과 그 적용

정재욱 ( Chung Jae - Wook ) 한국행정학회 1992 韓國行政學報 Vol.26 No.2

한-일 노인장기요양보험제도의 운영구조의 특징에 대한 비교 고찰

정재욱 ( Jae Wook Chung ) 한국지역발전학회 2009 지역발전연구 Vol.8 No.2

The Purpose of this paper is to examine the characteristics of operational structure of long-term care insurance system for the elderly of Korean and Japan. To accomplish this purpose, the framework which was made as four factor was formed. The finding results were shown as follows. The long-term care insurance system of korea retains more centralization system than that of Japan. In addition, the former keeps the simpler structure of service system than the latter. Therefore, to intend to institutionalize as the client-oriented system about the former, the extension of citizen participation would be requested relating to use service.

GF(p<SUP>m</SUP>)상에서 정의되는 타원곡선을 위한 복합 좌표계 응용

정재욱(Jae wook Chung),심상규(Sang Gyoo Sim),이필중(Pil Joong Lee) 한국정보보호학회 2000 정보보호학회논문지 Vol.10 No.1

타원곡선 이산대수 문제에 기초한 공개키 암호시스템에서 타원곡선 멱승은 반드시 필요한 연산이며 연산들 중에서 가장 복잡도가 크다. 따라서 효율적인 암호시스템 구현을 위해서는 타원곡선 멱승연산을 효율적으로 구현하는 것이 중요하다. 본 논문에서는 복합 좌표계(mixed coordinate system)를 이용한 멱승 방법을 GF(p<SUP>m</SUP>)상에서 정의되는 타원 곡선에 적용하여 최적의 효율성을 갖는 타원곡선 멱승 구현법을 제안한다. 또한 ‘곱셈을 이용한 역원 연산 알고리즘(IM; Inversion with Multiplication)’을 이용하여 더욱 효율적인 구현이 가능함을 보인다. In public key cryptosystems based on elliptic curve (EC) discrete logarithm problem, EC exponentiation is the most fundamental and also the most time-consuming function among EC functions. Thus it is important to implement efficient EC exponentiation to have an efficient EC cryptosystem. In this paper, we propose an efficient EC exponentiation algorithm which is optimized for GF(p<SUP>m</SUP>), by applying mixed coordinate technique. In addition, we show that a more efficient implementation is possible by utilizing `IM (inversion with multiplication), algorithm.

개인신용정보 공유 수준에 따른 금융회사 영향 분석: 부정적 및 긍정적 정보를 활용한 실증분석

정재욱 ( Jae Wook Chung ),함준호 ( Joon Ho Hahm ) 한국금융학회 2010 금융연구 Vol.24 No.3

본 연구에서는 국내 은행 및 카드사의 실제 개인신용 미시자료를 이용하여 금융회사가 부정적 및 긍정적 신용정보를 공유함에 따라 실현되는 경제적 효과를 실증 분석하였다. 분석 결과 금융회사는 자사정보만을 이용하거나, 은행연합회를 통해 공유되고 있는 기초정보만을 활용한 부분정보 모형에 비해, 긍정적 정보까지 모두 활용하는 경우 신용스코어 모형의 변별력이 유의하게 높아지며, 동일 승인율 하 불량률의 감소, 동일 불량률 하 승인율 및 여신규모(exposure)의 확대, 고객별로 차별화된 금리의 적용 등을 통해 위험관리의 실효성과 수익성을 제고할 수 있는 것으로 분석되었다. 이러한 결과는 소비자 입장에서도 정보의 비대칭성 완화에 따른 차입금리 하락과 여신 접근성 확대로 경제적 후생이 높아질 수 있음을 시사한다. 나아가 본 연구는 현실적으로 대형사와 중형사간 정보 보유량이 상이함을 감안하여, 긍정적 정보 공유의 효과가 금융회사의 규모에 따라 차별적으로 실현되는지 여부를 분석하였다. 분석 결과 통계적 성능지표의 향상, 동일 승인율 하 불량률 및 불량고객수 감소율, 동일 불량률 하 승인율 확대 효과 등, 모든 측면에서 대형사와 중형사간 긍정적 정보 활용의 효과가 유의한 차이 없이 실현되고 있는 것으로 나타났다. 이러한 결과는 일반적인 예상과는 달리 정보량이 많은 대형사가 정보공유에 따라 일방적으로 손해를 보는 구조가 아님을 의미한다. 이러한 현상은 우리나라의 경우 대형 금융회사의 고객일지라도 타사와 중복거래를 하고 있는 고객이 많기 때문인 것으로 판단되며, 대형사 또한 자사고객에 대한 타사의 정보를 활용하기 위해 적극적으로 정보공유에 나설 유인이 존재함을 시사한다. Currently in Korea, in addition to negative credit information such as loan default and arrears, positive credit information is also exchanged on a voluntary and reciprocal basis through private credit bureaus (CBs). This paper studies economic benefits of sharing negative and positive credit information realized by banks and credit card companies using individual consumer credit data of a large private credit bureau. We also investigate whether the degree of economic benefits that can be realized through positive information sharing is significantly different across financial companies with heterogeneous firm size. We find that, compared to the models based on each company`s own credit information or the basic and negative information compiled by the public credit registry, the performance of credit scoring models significantly improves when we utilize both negative information and positive information of credit bureaus. All statistical performance indicators such as Kolmogorov-Smirnov statistics, statistics, divergence, Gini index, and C-statistics improve significantly when positive information is utilized in addition to negative information for all sample banks and credit card companies regardless of their firm size. The improvement in discriminatory powers based on a wider set of credit information can produce significant economic benefits for financial companies. In our analysis of commercial banks, sharing positive credit information leads to a significantly lower default rate at each loan acceptance rate, and a higher loan acceptance rate and increased total exposure at each target default rate. We also obtained similar results for credit card companies. Hence, our results suggest that financial firms can substantially improve risk management capacity and enhance profitability by voluntarily sharing positive credit information. Our results also imply that positive information sharing can improve consumer welfare by alleviating asymmetric information problems as consumers` borrowing costs decrease and loan accessibility increases. We proceed to compare the benefits of positive information sharing across large and small financial companies. From every aspect such as statistical performance of credit scoring models, the degree of reduction in default rates and the number of defaulted obligors, and the increase in loan acceptance or card limit approval rates, we could not find significant differences in economic benefits realized across large and small financial companies. Hence, our results suggest that it is not necessarily a valid conjecture that large financial companies with a large customer base are hesitant to share their information voluntarily with small financial companies as their benefits are smaller relative to those of small companies. This finding reflects a notable feature of consumer credit markets in Korea. Namely, the customers of a large financial company tend to have multiple transaction relationships with other smaller financial companies. Hence, even large financial companies have a strong incentive to voluntarily share their positive credit information with smaller companies in order to obtain other companies` credit information on their own customers. Note that our empirical analysis assumes that the customer base of information sharing financial companies does not change subsequently as a result of credit information sharing. However, in reality, positive information sharing may increase competition and undermine profitability by lowering informational rents of financial companies. Hence, a financial company`s actual incentive to participate in the positive information sharing mechanism will depend upon the relative magnitude of economic benefits and costs resulting from enhanced risk management capacity and more intense competition. We leave this consideration of potential competition effects as a future research agenda.

생명보험 언더라이팅 시 개인신용정보의 활용 효과 분석

정재욱 ( Jae Wook Chung ),여윤희 ( Yoon Hui Yeo ) 한국금융연구원 2011 금융연구 Vol.25 No.1

Using accident and illness insurance applicants` data of a domestic life insurance company for a certain time period (2009. 1~7), we empirically examine if there exists a certain relation between individual credit information and accident rate. In other words, we analyze, step by step, the marginal effects of using individual credit information as an underwriting factor, in addition to existing internal underwriting criteria of an life insurance company, on the accuracy of accident rate forecasting. As a first step, we statistically prove that, the higher the individual credit rating (in terms of high-level, medium-level, and low-level) is, the lower the accident rate is. Second, to measure and compare the effects of predicting accident rate, we primarily derive three different logistic stepwise regression models, based on the scope of data employed (that is, “model 1”-a life insurer`s internal data only; “model 2”-data compiled by the KFB, in addition to a life insurer`s internal data; “model 3”-data compiled by the KCB, in addition to a life insurer`s internal data as well as data compiled by the KFB). First, on “model 1,” all the five variables from internal data have been safely selected. Those are gender, age, risk class, current number of policies owned, number of previous claim payments. Second, on “model 2,” two variables from KFB data have been selected additionally, along with five variables from insurance company`s internal data. Those two from KFB data are loan amount in banks and time since oldest credit opened. Third, on “model 3,” four variables from KCB data have been selected additionally, along with five variables from insurance company`s internal data, while any variables from KFB data have not been selected. Those four from KCB data are secured loan amount, percent of lump sum payment used in last one year, total number of delinquency substitute payment, and income. In the mean time, the unique direction of each selected variables was maintained in three dif- ferent models, and all the selected variables turned out to be statistically significant. Finally, we compares the results of accident improvement in each model to the bottom 2%, 5%, and 10% of high-risk group respectively. Our result shows the ranking as an order of “model 3” > “model 2” > “model 1” in terms of improving the accuracy of accident rate forecasting. It implies that a life insurer may have positive effects of reducing the accident rate by using individual credit information as an underwriting factor, thus eventually improving management efficiency.

유해산출물을 고려한 생명보험회사의 효율성 연구

정재욱 ( Jae Wook Chung ),김재현 ( Jae Hyun Kim ) 보험연구원 2008 보험금융연구 Vol.19 No.2

본 연구에서는 최근 4년간 우리나라 생명보험회사를 대상으로 유해산출물(효력상실·해약환급 금과 대손충당금적립 액)을 고려한 효율성(유해모델)과 유익산출물만을 사용한 전통적인 효율성(BCC모델)을 동시에 측정하여 비교 분석하였다. 분석결과 양쪽 모델의 효율적인 생명보험회사 수의 차이는 2003-2005년까지 비교적 유사하게 나타난 반면, 2006년에 이르러 그 차이가 크게 벌어진 것으로 나타났다. 한편 생명보험회사의 효율성이 증가할 수 있는 제반 요소의 변화가 있었음에도 불구하고 시간이 지남에 따라 생명보험회사의 효율성이 양쪽 모델에서 동시에 감소하고 있는 것으로 나타났다. 마지막으로 국내중소형생명보험회사의 효율성은 2003년 이후 전통적인 BCC모델에서의 효율성 우위가 점차 사라지고 있는 가운데 유해산출물을 고려한 유해모델에서는 오히려 외국생명보험회사보다 열위에 있는 것으로 나타났다. 결론적으로 이와 같이 상이한 분석결과는 향후 생명보험회사의 효율성 측정에 있어 유해산출물에 대해 보다 많은 관심을 가질 필요가 있음을 시사하고 있다. Firms, in general, produce not only desirable outputs, but also undesirable outputs such as toxic wastes and pollutants. While the standard DEA has been widely used employing only desirable outputs to measure firms`` efficiency, modified DEAs were developed to simultaneously deal with both desirable and undesirable outputs of the firm. This paper analyzes and compares the efficiency of life insurance companies using the standard DEA as well as a modified DEA model considering undesirable outputs: lapse and surrender refunds and loan loss reserve. The empirical results show that the number of efficient life insurance companies between the two models is different from year to year. In the meantime, the results find that the performance gap between efficient groups and inefficient groups has widened in both models, as time goes by. The results show, in particular, that small to mid-sized domestic life insurance companies are losing their competitive edge over foreign life insurance companies. In sum, such quite different empirical results between two models implicitly tell us that closer attention should be paid to undesirable outputs in the efficiency analysis of firms.