• Proceedings of the KSME Conference
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• 2007.05b
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• pp.1882-1887
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• 2007

In the present experimental study, the effect of interfacial tensions on pressure drop of air-water two-phase flow in round mini-channels was investigated. A glass (highly wettable) tube and a Teflon (poorly wettable) tube, both in 350 mm length but 1.8 mm and 1.59 mm in inner diameters each, were used for the tests. All the experiments were performed only in the plug flow regime, confirmed by visualization. In the glass tube, the gas plugs were surrounded by the liquid film along the inner periphery. On the other hand, the inner wall remained dry at the gas portion in the Teflon tube. The pressure drop of the plug flow in the Teflon tube without the liquid film) appeared much larger than in the glass tube (with the liquid film) due to dissipation of energy by movement of the wetting lines. In this paper, various correlations on the two-phase pressure drop of plug flows were compared and a modified correlation was proposed, taking account of the surface wettability.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.496-501
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• 2007

Recently, as MEMS and NEMS devices have been widely used in the various engineering applications, the characteristics of nanoscale systems are investigated in the limelight. However, as opposed to a macroscale system, the identification of the state of nanoscale systems is extremely hard because they can include only the order of $10^{3}\sim10^{5}$ molecules, which requires highly expensive and accurate experimental apparatus for an investigation. This limitations make the study on nanoscale system use computer simulations. Therefore, it is strongly required to identify the state of nanoscale system simulated in computer simulation. In these molecular dynamics(MD) study, we suggest that the potential energy of individual molecule can be used as criterion for defining the state of clusters or nanoscale systems. In addition, we compared the phase state from the potential energy with one from the radial distribution function(RDF) for verification. The comparison showed that the intermolecular potential energy can be used as a criteria distinguishing the phase state of nanoscale systems (This study will be published soon in the KSME transaction of the section B).

• Journal of Korea Multimedia Society
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• v.7 no.9
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• pp.1255-1262
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• 2004

This paper proposes a pattern matching algorithm which is useful for pattern matching and verification of images which includes noises. This algorithm is based on the feature that the signal energy of image is concentrated in a small frequency region in Fourier domain. The proposed method extracts the small parts around origins and compares the regions. Specifically, the parts around origins are extracted and subtracted, and finally experimental threshold is adopted for pattern matching. In particular, the proposed algorithm is useful for the images which includes noises because the noises are distributed in the high frequency region generally, and the method extracts the low frequency region only. Experimental result shows the method recognize ten standard images and three images includes various noises. This method shows the performance which is equal to or better than that of Phase Only Correlation in some cases.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.255-259
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• 2003

In this paper, we propose an improved image encryption and decryption method using a virtual image and a joint transform correlator (JTC). The encrypted image is obtained by the Fourier transform of the product of a virtual-phase image and a random-phase image, and a Fourier transform of the decrypting key generated by the proposed phase assignment rule is used as the Fourier decrypting key. Based on the solution, the original image is reconstructed using JTC in the frequency-domain. The proposed method using a virtual image, which does not contain any information from the original image, prevents the possibility of counterfeiting by unauthorized people. And also the auto-correlation terms, which are the drawback of a JTC system, contribute to reconstructing the original image rather than to disturbing its identification. But because phase-only encryptions are sensitive to noise and scratches, phase errors can be generated in fabricating the encrypted image or the Fourier decrypting key so the errors that are responsible for degradation of the quality of the reconstructed image are analyzed and the solution is demonstrated. Computer simulations show the solution, and the proposed method is very useful for JTC architecture.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.186-186
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• 2017

Relay intercropping system of direct seeded rice and winter cereal is labor saving cultivation and has high land use efficiency in Japan. In this system, rice seeds are direct seeded into inter-row space of winter cereals (wheat or barley) in March or April. If the direct seeding of rice is conducted before stem elongation phase or using suitable seeder, these are little effect to yield of winter cereals. Though the seeds are generally thiuram treated, it's a matter that seedling establishment rate (SER) of direct seeded rice is low and unstable. The cause of low SER has not been revealed. In present study, with the aim to reveal causes of low SER, we conducted experiments and investigated the SER, and analyzed some factors that might affect SER. Experiment1: In 2015, 2016, we buried rice seeds underground, and investigated the transition of the seed survival rates (SSR). Seeds were thiuram-treated or non-treated. In 2 periods, SSR of thiuram-treated seeds were significantly higher than non-treated seeds. In 2016, thiuram-treated seeds were high in SSR (almost 75%) at April 30th, but low SER (10~27%) after harvest of winter cereals. Therefore, almost all of seed death might have been happen after germination. Analysis 1: We investigated the SER and cultivation conditions in Ibaraki pref. for several years. Meteorological factors were referred from the nearest point of AMeDAS. From mean temperature (MT) among 5days after and before the day, we divided the period of seeding ~June 20 to phase1~4. We defined each phase as below; Phase1: $MT{\leq}10^{\circ}C$, Phase2: $10^{\circ}C<MT{\leq}15^{\circ}C$, Phase3:$15^{\circ}C<MT{\leq}20^{\circ}C$, Phase4: $MT>20^{\circ}C$. We analyzed the correlation of SER and meteorological factors by each phase. Total number of days in phase 1~4 was significantly negative correlated with SER. In phase1, total rain fall and number of soil wetting days were significantly negative correlated with SER. In phase2~4, only MT was significantly positive correlated with SER. This result suggested that rainfalls in phase1 declined seed vigor to emergence from soil surface, by repeated water absorption and re-dry. From these present studies, it was suggested that one of factors of low SER of direct seeded rice in relay intercropping system is changing of water condition by rainfalls in phase1 ($MT{\leq}10^{\circ}C$). To improve SER, it's necessary to consider something seed treatments such as prevent water absorption during phase1. However, 58~60% of seeds seemed to die during May. It's suggested that, if seeds are thiuram treated, almost all of seeds can germinate underground, but the seed vigor to emergence from soil surface are insufficient. Further studies are needed to reveal the rest causes that is happening during emergence from soil surface.

• Korean Journal of Biological Psychiatry
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• v.10 no.1
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• pp.70-79
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• 2003

Object : Currently, the alteration of cytokine system has been known to play an important role in regard to depressive symptom. We focused on the relationship between immunological parameters and clinical improvement in major depressive disorder. Method : Data were collected on 26 patients with major depressive disorder using a 8-week prospective follow-up design. After 8-week treatment period with fluoxetine, patients were classified into a response group and a non-response group according to their psychopathological outcome as evaluated by Hamilton Depression Rating Scale. The differences of the immunological parameters between pre-treatment phase and post-treatment phase were compared among patients. The difference of those was also compared within each phase among them. The relationship between socio-demographic variables, depression, cytokine, mononuclear cells was examined by correlation analysis. Multiple regression analyses were performed to explore the predictors of clinical improvement of major depressive disorder. Result : Pre-treatment levels of IL-$1{\beta}$ in the response group were significantly higher than those in the non-response group. Pre-treatment levels of IL-$1{\beta}$ of all patients and in the response group were positively correlated with pre-treatment monocyte counts. Patients with subsequent remission showed significantly lower IL-6 values at baseline than those with non-response. Post-treatment values of IL-6 did not differ significantly among the patients. The correlation test showed more frequent relations among cytokines and mononuclear cells in the response group than in the non-responder group. Especially, serum level of IL-6 in pre-treatment phase was only significantly correlated with HAMD score after 8-week treatement phase, while other cytokines and mononuclear cells were not. Pretreatment level of IL-6 was of paramount importance in predicting clinical improvement of depressive symptom. Conclusion : The immune system of major depressive disorder patients might dichotomize the patients into subsequent responders and non-responders. Immune system might be of great influence on the clinical improvement of major depressive disorder. The mode of interaction between depression and cellular immune function and the mediators responsible for the cytokine production need to be studied further.

• Research in Community and Public Health Nursing
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• v.26 no.4
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• pp.390-397
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• 2015

Purpose: The purpose of this study was to explore practice-based evidence for health promotion in vulnerable populations with hypertension in primary health care settings. Methods: Two methodological procedures were adopted for this triangulation study. In the first phase, the sample was obtained from the computerized clinical data repository of a community nursing center. A total of 286 clients were assessed for hypertension as an actual circulation problem as coded in the Omaha System. In the second phase, a qualitative focus group was surveyed through semi-structured interviews conducted by nine advanced practice nurses who had been serving the hypertensive patients. Results: The community nurses provided essential primary healthcare services including health teaching guidance and counseling, and surveillance to vulnerable populations living in medically underserved community. There was a significant positive correlation between knowledge and behavior (r=.53, p<.01), between knowledge and health status (r=.40, p<.05), and between behavior and health status (r=.48, p<.01). Conclusion: This triangulation study encompassed not only quantitative findings from the computerized records of clients but also other information acquired from advanced practice nurses. This study contributes to understanding the importance of health promotion nursing interventions even with populations already diagnosed with chronic diseases such as hypertension.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.502-513
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• 2004

This paper proposes a symbol synchronization method in the IEEE 802.11a wireless OPDM system, which uses only signs of the in-phase and the quadrature signals in the short preamble. The short preamble is sampled with 2 tines of Nyquist sampling rate and both of the autocorrelation and the cross-relation are used in the proposed method. This method has some advantages that the ACG (Automatic Gain Control) can be processed concurrently during the short preamble and its implementation is not much complicated. The proposed symbol synchronization method is verified through simulations on frequency offset, multi-path and white Gaussian noise.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6C
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• pp.623-628
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• 2006

This paper addresses the frequency offset estimation problem in the presence of the timing error for OFDM systems. When the timing error exists, the correlation value used for the frequency offset estimation could be reduced significantly due to the timing error, resulting in considerable degradation in estimation performance. In this paper, using the coherence phase bandwidth (CPB) and a threshold, a novel frequency offset estimation scheme is proposed and based on which, an efficient timing error estimation scheme is also proposed for the re-estimation of the frequency offset. The performance comparison results show that the proposed frequency offset estimation scheme is not only more robust to the timing error but also has less computational complexity, as compared with the conventional schemes. It is also demonstrated by simulation that theproposed timing error estimation scheme gives a reliable estimate of the timing error.

• Journal of Communications and Networks
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• v.15 no.3
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• pp.276-282
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• 2013

Self-encoded spread spectrum (SESS) is a novel modulation technique that acquires its spreading code from a random information source, rather than using the traditional pseudo-random noise (PN) codes. In this paper, we present our study of the SESS system performance under pulsed-noise jamming and show that iterative detection can significantly improve the bit error rate (BER) performance. The jamming performance of the SESS with correlation detection is verified to be similar to that of the conventional direct sequence spread spectrum (DSSS) system. On the other hand, the time diversity detection of the SESS can completely mitigate the effect of jamming by exploiting the inherent temporal diversity of the SESS system. Furthermore, iterative detection with multiple iterations can not only eliminate the jamming completely but also achieve a gain of approximately 1 dB at $10^{-3}$ BER as compared with the binary phase shift keying (BPSK) system under additive white gaussian noise (AWGN) by effectively combining the correlation and time diversity detections.