• Communications of the Korean Mathematical Society
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• v.12 no.2
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• pp.479-490
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• 1997

We consider long nonlinear waves in the two-layer flow of an inviscid and incompressible fluid bounded above by a free surface and below by a rigid boundary. The flow is forced by a bump on the bottom. The derivation of the forced KdV equation fails when the density ratio h and the depth ratio $\rho$ yields a condition $1 + h\rho = (2-h)((1-h)^2 + 4\rho h)^{1/2}$. To overcome this difficulty we derive a forced modified KdV equation by a refined asymptotic method. Numerical solutions are given and hydraulic fall solution of a two layer fluid is expressed analytically in the case that derivation of the forced KdV (FKdV) equation fails.

• Journal of Industrial Technology
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• v.29 no.B
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• pp.107-113
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• 2009

For the environmental safety of the operating room and patient healthcare, the closed type rebreathing system is widely adopted. In order to reduce the anesthesia gas during surgery, the mixing ratio of anesthesia gas with breathing air should be precisely controlled. Generally, the breathing air passes through the vaporizer to mix the anesthesia gas, but there is a difficulty in controlling the mixing ratio precisely. In this paper, the stand-alone style vaporizer is designed and the operating characteristics are investigated. The vaporizer measures the temperature and pressure in the vaporizing chamber and chamber temperature is precisely controlled by proportional controlled heater. Exact quantity of anesthesia media is feeded by PID controlled peristaltic pump and vaporized gas is mixed with breathing air flow by PWM controlled solenoid valve. The experimental result shows that the vaporizer has an excellent command following performances that it can be applied to the low flow anesthesia system.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1777-1782
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• 2003

This paper presents the design, fabrication, and testing of the capillary-induced pressure drop valve, thermocapillary pumping of liquid droplet in hydrophilic channels and the splitting of droplet. The capillaryinduced pressure drop is derived with thermodynamic approach considering three-dimensional meniscus shape which is essential for calculating pressure drop in the diverging shape channel when the aspect ratio is close to one. The micro channel is fabricated via MEMS processes, which consists of the liquid stop valve to retard the liquid droplet, thermocapillary pumping region and the bifurcation region. Also the micro heaters are fabricated to drive the droplet by thermocapillary. The theoretical approaches agree well with the experimental data. The functionality of capillary valve is confirmed to be valid when the aspect ratio is smaller than one. To overcome the difficulty in splitting of the droplet due to the pressure drop in the general Y-shape channel, the protrusion shape is employed for easy splitting in the bifurcation channel.

• Journal of computational fluids engineering
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• v.2 no.1
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• pp.129-137
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• 1997

We consider long nonlinear waves in the two-layer flow of an inviscid and incompressible fluid bounded above by a free surface and below by a rigid boundary. The flow is forced by a bump on the bottom. The derivation of the forced KdV equation fails when the density ratio h and the depth ratio ρ yields a condition 1＋hρ=(2-h)((1-h)²＋4ρh)/sup 1/2/. To overcome this difficulty we derive a forced modified KdV equation by a refined asymptotic method. Numerical solutions are given and hydraulic fall solution of a two layer fluid is expressed analytically in the case that derivation of the forced KdV(FKdV) equaition fails.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.1
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• pp.20-33
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• 2015

Spectrum sensing is a key component of cognitive radio. The prediction of the primary user status in a low signal-to-noise ratio is an important factor in spectrum sensing. However, because of noise uncertainty, secondary users have difficulty distinguishing between the primary signal and an unauthorized signal when an unauthorized user exists in a cognitive radio network. To resolve the sensitivity to the noise uncertainty problem, we propose an entropy-based spectrum sensing scheme to detect the primary signal accurately in the presence of an unauthorized signal. The proposed spectrum sensing uses the conditional entropy between the primary signal and the unauthorized signal. The ability to detect the primary signal is thus robust against noise uncertainty, which leads to superior sensing performance in a low signal-to-noise ratio. Simulation results show that the proposed spectrum sensing scheme outperforms the conventional entropy-based spectrum sensing schemes in terms of the primary user detection probability.

• ETRI Journal
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• v.46 no.1
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• pp.106-117
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• 2024

Large language models (LLMs) have revolutionized various applications in natural language processing and exhibited proficiency in generating programming code. We propose a framework for evaluating the code generation ability of LLMs and introduce a new metric, pass-ratio@n, which captures the granularity of accuracy according to the pass rate of test cases. The framework is intended to be fully automatic to handle the repetitive work involved in generating prompts, conducting inferences, and executing the generated codes. A preliminary evaluation focusing on the prompt detail, problem publication date, and difficulty level demonstrates the successful integration of our framework with the LeetCode coding platform and highlights the applicability of the pass-ratio@n metric.

• The KIPS Transactions:PartD
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• v.9D no.1
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• pp.75-80
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• 2002

Putnam develops SLIM (Software LIfecycle Management) model based upon the assumption that the manpower utilization during software project development is followed by a Rayleigh distribution. To obtain the manpower distribution, we have to be estimate the total development effort and difficulty ratio parameter. We need a way to accurately estimate these parameters early in the requirements and specification phase before investment decisions have to be made. Statistical tests show that system attributes are highly correlation (redundant) so that Putnam discards one and get a parameter estimator from the other attributes. But, different statistical method has different system attributes and presents different performance. To select the principle system attributes, this paper uses the principle component analysis (PCA) instead of Putnam's method. The PCA's results improve a 9.85 percent performance more than the Putnam's result. Also, this model seems to be simple and easily realize.

• Journal of Science Education
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• v.36 no.2
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• pp.293-302
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• 2012

The purpose of this study was to analyze of the science examination of middle school 7th grade by Klopfer's taxonomy of educational objectives. A total of 645 test items from 10 middle schools were analyzed for this study. The examination items were analyzed according to the objectives of science education, such as behavior and contents area, question types, and the degree of difficulty. It was shown that, when the distribution of behavioral objectives was considered, the items emphasized knowledge and comprehension, and were scientific knowledge oriented. The tests consisted of multiple choice questions at a relatively high rate, compared to short answer questions. Comparing the rate of teachers' expectations to the degree of difficulty, the ratio of "top" was low and that of "medium" was high. The results of this study suggested that using various types of question and multiple levels of content and behavior enabled more effective evaluation of the diverse thinking powers and learning of the students.

• Journal of Korean Academy of Nursing
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• v.46 no.3
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• pp.400-408
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• 2016

Purpose: This study was done to identify frequency, intensity of urinary dysfunction and daily life distress in women after a radical hysterectomy for cervical cancer. Methods: One hundred and fifty seven women who had undergone a radical hysterectomy and one hundred and sixty five women as healthy controls completed questionnaires on intensity of urinary dysfunction and daily life distress caused by urinary dysfunction. Results: Women with cervical cancer showed higher frequency of urinary dysfunction than healthy controls. Major urinary dysfunction for women with cervical cancer in order of frequency were night-time incontinence (odds ratio=10.39, p<.001), difficulty in starting urination, weak urine stream and sense of incomplete emptying of bladder. The highest score on intensity was difficulty in starting urination, followed by urgency, weak urine stream, daytime frequency and sense of incomplete emptying. Night-time incontinence was the urinary symptom causing the most daily life distress for cervical cancer women followed by difficulty in starting urination, urgency, sense of incomplete emptying, and night-time frequency. Conclusion: Results suggest that nurses should address the potential postoperative urinary complications and develop long term interventions to decrease urinary dysfunction and daily life distress for women who have had a radical hysterectomy for cervical cancer.

• Speech Sciences
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• v.11 no.2
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• pp.105-117
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• 2004

Recently, many scholars have emphasized the importance of English listening ability for smoother communication. Most audio materials, however, were recorded in a quiet sound-proof booth. Therefore, students who have spent so much time listening to the ideal audio materials are expected to have difficulty communicating with native speakers in the real life. In this study, we examined how well thirty three Korean university students and five native speakers will repeat the recorded English sentences under noise and speed conditions. The subjects' production was scored by listening to each recorded sentence and counting the number of words correctly produced and determined the percent ratios of correctly produced words to the total words in each sentence. Results showed that the student group correctly repeated around 65% of all the words in each sentence while the native speakers demonstrated almost perfect match. It seemed that the students had difficulty perceiving and repeating function words in various conditions. Also, high-proficiency student group outperformed the low-proficiency student group particularly in their repetition of function words. In addition, the student subjects' accuracy of repetition remarkably dropped when the normal sentences were both sped up and mixed with noise. Finally, it was observed that the Korean students' percent correct ratio fell down as the stimulus sentence became longer.