• 유통과학연구
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• 제21권2호
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• pp.77-89
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• 2023

Purpose: At the end of the pandemic, many digital startups had negative performances. For that, this study aims to analyze the mediating role of entrepreneurial competence and digital entrepreneur career maturity. Seven hypotheses were proposed, namely the effect of entrepreneurship orientation, digital entrepreneurship experience, and digital entrepreneur career maturity on digital entrepreneurial competence, the effect of digital entrepreneurial experience on digital entrepreneurial career maturity, the influence of entrepreneurial orientation, entrepreneurial competence, and digital entrepreneur career maturity on business performance. Research design, data and methodology: The population is digital entrepreneurs in Central Java, Indonesia with a business duration of more than 4 years. The number of samples as many as 184 people were carried out by questionnaire distribution through face-to-face, email, and Google forms. Partial Least Square Structural Equation Modeling was used to test the path coefficient statistics. Results: The results showed that all the hypotheses proposed were accepted. Digital entrepreneurial competencies and digital entrepreneurial career maturity are also proven to have a mediating role. Conclusions: The findings of this study can contribute to the development of digital entrepreneurship research. Practically, the government's role is needed to facilitate the three main elements of digital business: e-commerce, payment methods, and distribution channels.

• JSTS:Journal of Semiconductor Technology and Science
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• 제7권1호
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• pp.28-35
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• 2007

This paper presents a high-speed flash analog-to-digital converter (ADC) for ultra wide band (UWB) receivers. In this flash ADC, the interpolating technique is adopted to reduce the number of the amplifiers and a linear and wide-bandwidth interpolating amplifier is presented. For this ADC, the transistor size for the cascaded stages is inversely scaled to improve the trade-off in bandwidth and power consumption. The active inductor peaking technique is also employed in the pre-amplifiers of comparators and the track-and-hold circuit to enhance the bandwidth. Furthermore, a digital-to-analog converter (DAC) is embedded for the sake of measurements. This chip has been fabricated in $0.13{\mu}m$ 1P8M CMOS process and the total power consumption is 113mW with 1V supply voltage. The ADC achieves 4-bit effective number of bits (ENOB) for input signal of 200MHz at 5-GSample/sec.

• 전자공학회논문지D
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• 제36D권5호
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• pp.36-43
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• 1999

새로운 방식의 직접 디지털 주파수 합성기(Direct Digital Frequency Synthesizer, DDFS)의 설계방식을 제시하였다. 배열형 CORDIC(Coordinate Rotate Digital Computer)을 해석함에 있어서 오차의 크기를 계산하였다. 오차에는 계산회수의 부족에서 발생하는 ‘반복회수오차’와 제한된 데이터 비트수를 사용함으로써 계산에 사용하지 못하는 유효숫자 이하를 버림으로써 발생하는‘절단오차’로 분류할 수 있다. 실제로 각 비트별로 오차를 측정해 보면 8비트시 7단, 16비트시 12단, 24비트시 20단으로 근최적화된 파이프라인 단수를 얻을 수 있었다. 이 DDFS는 FPGA칩으로 구현되었고, 측정결과 235MHz의 구동 클럭에서 안정된 동작을 보였으며, 11.75MHz의 최대 출력 주파수를 발생시켰다. 위상별 진폭값을 ROM에 저장하는 기존의 방식에 비하여, 보다 높은 정밀도와 처리속도를 보이며, 제조공정 역시 단순해 질 것이다. 특히 같은 비트를 채택한 경우 롬방식에 비하여 5배정도의 높은 정밀도를 얻었다.

• 한국분무공학회지
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• 제14권2호
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• pp.77-83
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• 2009

In this study, the effect of important parameters such as the pixel size and number of a CCD, the object distance, the wavelength of laser, and the particle diameter on the depth of focus in digital in-line particle holography were investigated. The depth of focus in several different cases was calculated using simulation holograms and detailed description of the depth of focus in digital particle holography was presented. The depth of focus is directly proportional to the object distance and the particle size. With the increase of the wavelength of laser, the depth of focus is decreased. The depth of focus is also inversely proportional to the pixel size and number of a CCD. Using the data of depth of focus from simulation holograms and a data-fitting software, we obtained the prediction equations of depth of focus for typical CCD cameras. Finally, the prediction equations of depth of focus in digital particle holography were verified by investigating real holograms of the calibration target in different cases and satisfied agreement between measured values and predicted values was confirmed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.628-649
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• 2017

Security and resource-saving are both demands of the fifth generation (5G) wireless networks. In this paper, we study the secrecy spectrum efficiency (SSE) and secrecy energy efficiency (SEE) of a K-tier massive multiple-input multiple-output (MIMO) enabled heterogeneous cellular network (HetNet), in which artificial noise (AN) are employed for secrecy enhancement. Assuming (i) independent Poisson point process model for the locations of base stations (BSs) of each tier as well as that of eavesdroppers, (ii) zero-forcing precoding at the macrocell BSs (MBSs), and (iii) maximum average received power-based cell selection, the tractable lower bound expressions for SSE and SEE of massive MIMO enabled HetNets are derived. Then, the influences on secrecy oriented spectrum and energy efficiency performance caused by the power allocation for AN, transmit antenna number, number of users served by each MBS, and eavesdropper density are analyzed respectively. Moreover, the analysis accuracy is verified by Monte Carlo simulations.

• 한국수학사학회지
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• 제12권2호
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• pp.47-54
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• 1999

We introduce some historical facts on number theory, especially prime numbers and modular arithmetic. And then, with the viewpoint of computer arithmetic, residue number systems are considered as an alternate to positional number systems so that high performance and high speed computation can be achieved in a specified domain such as cryptography and digital signal processing.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2003년도 추계학술발표회 논문집
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• pp.219-224
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• 2003

Recently, the number of the use of Digital Photogrammetry is increasing, the Digital Photogrammetry is used for the acquisition of images, remote sensing and three dimension location. Especially, the three dimension location is more activated to use digital camera for the Digital Photogrammetry. The reason is that it is cheap and easy to use and also it has high confidence. Using non-metric digital camera not metric camera, in this research, to get images and apply the images to the Direct Liner Transformation which is one of the techniques in Digital Photogrammetry to get three dimensional location of a point. Ⅰ programmed the procedure with Visual C++ to get the position of points speedly and I tested possibility whether it can analyze the displacement and the existence of structure with measurement system which is structured by a inexpensive non-metric digital camera.

• 디지털산업정보학회논문지
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• 제5권2호
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• pp.109-121
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• 2009

As our society is changed to the information & digital society based on the internet, the requirement that the analog certificate of Korean residence is changed to digital one is increased. The Korean Government selected the smart card of 72 KB for the digital certificate of Korean residence and try to insert the personnel information of 41 items to it. The method that the numerous personnel information is stored in one smart card is convenience to use. If the certificate of residence is lost, the number of personnel information is misused or spreaded thorough the Internet by the hacking. In this paper, we analyze the problem about the digital certificate of Korean residence and propose the countermeasure about the problem. In the proposal, the digital certificate of residence have only the certificate. Therefore, the size of the smart card is minimized and can be canceled at the loss of the certificate of residence. And the exposure worry of personnel information will be decreased.

• International Journal of Computer Science & Network Security
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• 제22권2호
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• pp.297-303
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• 2022

The main purpose of the study is to determine the main aspects of the problem of socio-economic development in the conditions of the digital economy. The post-industrial era is characterized by the development of the electronic environment and the transition to an information civilization. In this regard, the developed countries of the world pay considerable attention to the development of the digital economy. However, there are a significant number of problems associated with this process. The country cannot be successful in the development of the digital economy in the absence of the necessary legal framework, an economic development strategy based on digital technologies. The research methodology involves the use of several theoretical methods for analyzing and synthesizing information. As a result of the study, the key problems of socio-economic development in the digital economy were characterized.

• Archives of Reconstructive Microsurgery
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• 제8권1호
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• pp.44-49
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• 1999

From January 1990 to December 1998, 449 consecutive single-digital replantations were reviewed retrospectively in order to determine the essential number of vascular anastomoses for successful finger replantation. The correlations between the number of anastomosed vessels and survival rate were examined according to the amputated digital levels and all of the correlated results were compared with each other statistically. In zone I, The survival rate of the digits with a repaired vein was higher than that of digits treated with external bleeding method. In zone II, the equal number(s) between the arterial and venous repair was an important factor in successful replantation. And the repaired arteries more than repaired veins in number led to venous congestion and resulted in a failure of replantation, which was maybe due to the large amount of arterial input relative to small volume of amputated stump with small sized vein. In zone III, the equal number(s) between the arterial and venous repair was also an important factor in successful replantation. But unlike in zone II, venous congestion was scarcely happened if the venous drainage was sufficient with a repaired large vein alone. In zone IV, two or more arteries and veins were required for successful replantation. In conclusion, it is desirable that the repair of vessels as many as possible to increase the possibility of a good result. But digital amputations and their condition for replantation were variable, therefore, the numbers in vascular repair should to be modified and straightforward as the case may be.