중국 대학생의 해양 리터러시가 친해양 환경 행동에 미치는 영향 연구

WANG LINZHAO 국립부경대학교 대학원 2025 국내박사

This study aims to explore the impact of ocean literacy among Chinese university students on pro-marine environmental behaviors and to analyze in depth how marine environmental responsibility, marine environmental values, and marine environmental beliefs mediate this process. Employing a mixed-methods research strategy, the study conducted a quantitative survey of 860 students from ten universities across Guangdong, Henan, and Hubei provinces, along with in-depth qualitative interviews with 16 students, to construct a comprehensive model examining the relationships among these variables. The quantitative part of the research utilized a parallel mediation model to thoroughly analyze the direct impact of ocean literacy on Chinese university students' pro-marine environmental behaviors and its potential mediating effects. This model revealed the critical mediating roles of marine environmental responsibility and values in bridging ocean literacy with pro-environmental behaviors. Analysis of questionnaire data from 860 students showed that most lacked awareness of marine conservation, and overall levels of ocean literacy were relatively low. However, the data also indicated that as ocean literacy improved, students' recognition of the importance of marine conservation significantly increased. This enhanced awareness not only spurred students' sense of marine environmental responsibility but also helped shape and strengthen positive environmental values, thereby significantly promoting their environmental actions. The findings further emphasize the central bridging role of marine environmental beliefs in developing ocean literacy and driving pro-marine environmental actions. By enhancing the public's, especially young students', deep understanding of marine issues, a more intense sense of environmental responsibility and more active conservation behaviors can be effectively stimulated. This internally driven force is not only rooted in the cultivation of marine environmental values but also involves how to combine personal and societal interests, thereby comprehensively enhancing individual environmental awareness and facilitating a transformation in environmental behaviors. The qualitative part of this study involved in-depth interviews with 16 university students using NVivo software, followed by systematic coding analysis of the interview results. These analyses supplemented the findings from the quantitative study, revealing the complexities of students' multidimensional cognition, attitudes, and behaviors toward marine conservation. The analyses demonstrated that the environmental behaviors of Chinese university students are influenced not only by their marine science knowledge but also by a combination of factors including environmental ethics, personal values, and socio-cultural backgrounds. The interview data further revealed students' profound understanding of marine ecosystems and their strong sense of responsibility toward marine conservation, deeply influenced by their values and environmental beliefs. During the interviews, students expressed challenges in translating environmental awareness into concrete actions, such as limitations in resources and opportunities and constraints imposed by cultural and social structures. In summary, this research constructed a theoretical and empirical model by comprehensively analyzing the relationships between ocean literacy, marine environmental values, marine beliefs, marine responsibility, and pro-marine behaviors, thus deeply revealing how these variables interact to promote environmental actions. The study employed a mediation model form, not only deepening the understanding of how ocean literacy directly impacts pro-marine behaviors but also clarifying the critical mediating roles of marine responsibility and values in this process. The study showed that enhancing ocean literacy significantly boosts individuals' recognition of the importance of marine environmental protection. This recognition, by stimulating marine responsibility and shaping positive environmental values, significantly drives environmental actions. Furthermore, the strengthening of marine beliefs has been proven to be an effective way to enhance public ocean literacy, which can stimulate a stronger sense of environmental responsibility and proactive conservation behaviors through enhanced awareness and understanding of marine issues. The theoretical and practical findings of this study provide a new perspective for expanding the research framework on pro-marine environmental behaviors and offer new mechanisms on how ocean literacy can influence environmental actions through mediating variables. On a practical level, these findings provide a basis for formulating targeted educational and policy measures, helping to promote more effective environmental protection actions and thus facilitating the development of sustainable management and conservation strategies for marine resources. This study also has certain limitations, such as the geographic and cultural representativeness of the sample and the cross-sectional study design, which limits the in-depth analysis of causal relationships. Future research should expand the sample size and adopt a longitudinal design to explore the causal relationships between ocean literacy and pro-marine behaviors. Additionally, combining multiple research methods could reduce biases and enhance the reliability of the data. Further research into the mechanisms of marine values and through education, policy, and social support, helping students overcome practical barriers could promote more effective environmental behaviors and sustainable management of marine resources. These research efforts will provide solid theoretical support for understanding the complex relationships between ocean literacy and pro-marine behaviors and offer practical guidance for marine education and policy formulation.

U-헬스케어를 위한 의복형 심전도 및 호흡신호 계측 시스템 설계 및 구현

박영빈 경북대학교 대학원 2016 국내석사

According to statistics Korea, the number of people with respiratory problems and cardiovascular disease is increasing. Especially, young children, oldster and chronic patients, who have asthma, cardiac insufficiency, and so on, need to be often measured their ECG and respiratory signal. However it is inconvenient because they have to visit hospital and current bio- signal instruments are not useful in daily lives. In the study, a convenient sensor for respiratory signal and ECG device was made using conductive fabric. The device has form of clothes. Thereby, it will be wearable and useful in daily lives. The sensor for respiratory signal consist of parallel rectangular plate which was made of conductive fabric. In this device, a constant-current source was selected for non-contact measurements of capacitance variations due to respiration. So, The sensor measures varying capacitance caused by movement of back muscles due to respiration. The sensors for ECG signal are attached at wrists of coat and measures voltage difference of wrists. After the respiratory signal and ECG signal are processed by electronic circuits, the wave forms of signal are graphically displayed on a smart phone. Using the proposed device, each respiratory signal was measured in various exercise conditions and ECG signal is verified by analysis of waveform.

이식형 의료기기로 인한 MRI영상의 인공음영 축소를 위한 외부 코일 시스템 설계

안형준 경북대학교 대학원 2016 국내석사

Recently, several implantable medical devices have a power receiving module from outside the body, such as a cochlear implant which are frequently used to treat the hearing impaired patients. Most of implantable medical devices are adopted magnet pairs to couple between internal and external devices for the enhancement of power transmission. Usually, the internal device which containing a magnet in the center of receiving coil is implanted under the skin of the temporal bone. In case of MRI scanning to a patient who has such implant, the static magnetic fields of the MRI might be interfered by the fields of the implanted magnet in the skin. From the reasons above, the image from MRI is degraded by large area of artifact, so that diagnostics are almost impossible in deteriorated region. In this paper, we propose an external coil that can compensate the magnetic fields due to the internal coupling magnet. By applying the optimum current in the external coil, it can produce optimum cancellation magnetic field for these interferences. And finally, the effectiveness of the proposed coil by using MRI and finite element analysis is verified.

Studies of Various TMRs on the Characteristics of Ruminal Fermentation and Degradability by Rumen Microbes

Lee, Seung Uk 충북대학교 2015 국내석사

A metabolic trial was conducted with two ruminally cannulated cows in a 3 x 3 Latin Square design with three periods to investigate the effects of three total mixed ration (TMR) on the fermentation characteristics and effective degradability(ED) by rumen microbes. In the present study, the three feeds for beef cattle were growing stage TMR (GR-TMR), early fattening stage TMR (EF-TMR) and late fattening stage TMR (LF-TMR). The present in vitro trial for the TMRs before and after extraction was made an-aerobically in the mixed solution consisting of strained rumen fluid and artificial saliva (1:1, v/v) at 39℃ up to 48 hours. The pH in incubation solution tended to decrease up to 48h, but the opposite results were found in concentration of total gas production, ammonia-N and total VFA. The total gas production and total VFA production in LF-TMR was higher than the others TMRs. The EDDM in both EF-TMR and LF-TMR was higher compared with GR-TMR. The results of the present in vitro study indicate that TMR may provide more favorable condition for nutrient digestion in the rumen. 본 연구에 사용된 사료는 고급육 개발을 위한 사양실험에 사용된 사료로서 그 근거를 위한 반추미생물에 의한 대사적 평가를 위해 실시되었다. 시험을 위하여 반추위 누관이 장착된 홀스타인 두 마리를 이용하였고, in vitro 실험에 사용된 사료(처리구)는 사양단계에 따라 TDN 수준이 달리 배합된 육성기, 비육전기, 비육후기 사료를 사용하였다. In vitro 실험을 실행하기 일주일전부터 건유기 사료 (5.6kg/d)와 조사료 (볏짚, 2.4kg/d)를 급여하여 적절한 반추위 환경이 조성되도록 하였다. 실험 당일 아침 사료 급여 2시간 후에 위액을 채취하여 거즈를 통해 사료입자를 걸러내고 배양병에 인공타액과 1:1 비율로 혼합한 후 혐기적 상태, 39℃에서 분당 135회의 진탕속도로 배양하였다. 배양이 시작되고 난 뒤 1, 3, 6, 12, 24, 48시간에 pH와 가스발생량을 측정하고, 암모니아와 VFA 분석을 위하여 각각 1ml과 0.8ml을 채취하여 냉동 보관하고실험 종료 후 일괄적으로 분석을 실시하였다. 배양이 시작되고 시간이 경과될수록 모든 처리구에서 pH가 지속적으로 저하되었다. 시간당 가스발생량은 비육후기 사료에서 가장 높았으며, 누적된 가스발생량 또한 비육후기 사료에서 가장 높았다. 암모니아의 농도는 전체적으로 유의적 차이는 보이지 않았지만 비교적 단백질 함량이 다소 높았던 비육전기와 비육후기 사료에서 높은 경향이었다. 배양액 내의 총 VFA 생성량은 유의적인 차이는 없었지만 비교적 TDN 함량이 높은 비육후기 사료에서 높게 조사되었다. 각 사료를 나일론백을 이용하여 측정한 건물 유효 분해율은 유의적 차이는 보이지 않았지만 비육전기와 비육후기 사료에서 비교적 분해율이 높은 경향이었으며, 초기 쉽게 분해 될 수 있는 “a” 값 역시 비육전기와 비육후기 사료에서 높게 조사되었다(P<0.05). 본 연구를 통해 한우 성장단계에 따른 TDN 함량이 다른 TMR 사료는 반추위 미생물에 의한 가스 발생량을 포함한 발효특성에 영향하는 것으로 조사되었다. 에너지 밀도가 높을수록 발효산물이 많이 발생되며, 가스도 많이 생성되는 경향이었다. 이로 미루어 볼 때, 실제 반추가축의 반추위 내에서도 같은- 36 - 경향으로 반추위 미생물에 의한 발효가 진행될 것으로 예상된다. 따라서 반추가축에게 TMR 사료를 급여하는 것은 영양적인 대사를 개선함과 동시에 이상적인 반추위 발효환경을 조성하는데 기여 할 것으로 사료된다.

정원창 구동 이식형 인공중이를 위한 3-코일 벨로우즈 트랜스듀서

신동호 경북대학교 대학원 2016 국내박사

Various kinds of hearing aids have been utilized to overcome hearing impairment in humans, and nowadays, many types of hearing aids are available for patients with different types of hearing loss. Recently, a new method in which the transducer is installed at the round window (RW) has been widely investigated because this method can solve the problem of ossicle necrosis and is also useful in cases without ossicles. The Carina model developed by Cochlea, Inc. is installed at the RW using a ball tip which connected at transducer. But, the Carina is implanted at inside wall of temporal bone because the transducer is large size. For this reason, implant surgery is complicated and difficult. The Vibrant Soundbridge (VSB) produced by MED ‒ EL, Inc. The VSB is involved wrapping the FMT using a biological fascia that maintains proper contact with the RW membrane and then positioning it in the niche of the RW. But, according to several studies, the RW ‒ drive method using a FMT has a notably low vibration gain in low-frequency regions. To solve these issues, the new structures of RW transducer with the ease of implantation are necessary. In this paper, a new tri-coil bellows transducer (TCBT) has been proposed for RW middle-ear hearing devices. The proposed TCBT can overcome the weak points of the existing transducer and its smaller size than existing transducer helps easy to implant at the RW. This transducer consists of three cylindrical coils, a three-pole magnet, and a miniaturized bellows. This scheme maximizes magnetic field utilization efficiency and reduces the interference of the environmental magnetic field. To determine the characteristics of the proposed TCBT, mechanical and electrical simulation was performed, and then a comparative analysis of the fixed type transducer and floating mass type transducer was done. The simulations of the unloaded frequency characteristics showed that the fixed type transducer has remarkably higher output than the floating mass type transducer in whole frequency range. The loaded fixed type transducer’s velocity output decreased by only 6dB relative to the unloaded case at 100 Hz, whereas at the same frequency the loaded floating mass type transducer’s velocity output decreased by over 22dB relative to the unloaded case. In the high-frequency range, the two devices showed similar attenuation characteristics in response to RW loading but attenuation of fixed type transducer has slightly higher than floating mass type transducer at 3 kHz. The structure of bellows can be designed by means of mechanical vibrational characteristics using the finite element analysis. In the case of a TCBT that is attached to the RW, resonance characteristics must be generated near the 2 kHz band in order to obtain characteristics similar to the transmission characteristics of the middle-ear. The stiffness of bellows is changed according to the geometric and the number of corrugation to obtain similar the frequency characteristics of human ear. The results of the FEA simulation indicated that the optimum frequency characteristics of the bellows were as follows: a 68% ratio for the inner and outer diameters of the bellows with a 7.6 µm thickness and 3 corrugations. Based on these simulation results, the TCBT has implemented that has far better excellent low-frequency characteristics than the FMT. And, distortion of the fabricated transducer for performance verification was measured using the distortion meter. As a result, the distortion of loaded case showed 1.2% at resonance frequency and 1% or less at other frequency bands. To evaluate the characteristics of this newly developed TCBT, the transducer was installed in the RW niches of five human cadaver temporal bones and the velocity of the stapes footplate was measured. The RW stimulation measurements made by driving the TCBT with 2 mW showed that the stapes vibration below 1 kHz, 1~3 kHz and above 3 kHz produced 100, 111 and 129dB SPL equivalent pressure outputs, respectively. Thus, it is expected that a TCBT with one side coupled to the RW via a tiny elastic bellows and the non-vibrating other side fixed to the bone of the RW niche will be both easy to implant and offer better performance over the others transducer in terms of frequency response and power efficiency.

실시간 successive-FFT 방식의 WDRC에 의한 완전 이식형 저전력 초소형 인공중이 전용 프로세서 설계

김동욱 경북대학교 대학원 2014 국내박사

Recently, the population of hearing impaired people is increasing continuously and many people suffer from their hearing problems. To dealing with this problem, the various type hearing aid are being rapidly developed. Especially, the fully-implantable middle ear hearing device (F-IMEHD) is actively studied for sensorineural hearing loss people. The basic F-IMEHD system consists of implantable microphone, signal processor, and vibration transducer. The signal processor design must consider the input and output characteristics such as microphone output level and resonance of vibration transducer. In addition, signal processor had to accomplish the small size and low power consumption for implantation. In this paper, we designed and implemented the small size and low power consumption signal processing chip for the F-IMEHD system. The designed chip consists of analog to digital converter (ADC), multi-channel wide dynamic range compression (WDRC), wireless communication, and output stage. In order to achieve the small size and low power consumption, we adopt the successive approximation register (SAR) ADC. The designed SAR ADC has 16 bit data resolution and operates on the 32 kHz sample rate. To verify the designed SAR ADC, the computer simulations and analog layout with the consideration of application specific integrated circuit (ASIC) have been performed. For the simulation, the Spectre (Cadence, USA) is used in a 0.18 ㎛ CMOS process library. Also, analog layout is designed by Virtuoso (Cadence, USA) and the dimension of designed SAR ADC are the width of 133.9 ㎛ and the length of 98.3 ㎛. The multi-channel WDRC is designed as 4-channel system to adapt the frequency resonance of transducer. The frequency channels are separated to use 64 point FFT method. To reduce the amount of computation and memory utilization, FFT algorithm for frequency analysis is implemented without using the phased information of twiddle factor. The proposed WDRC algorithm based on the successive-FFT is not performs inverse FFT which have summation and multiplication for signal reconstruction. The proposed successive-FFT used repetition of the twiddle factor and it calculates only data summation for signal reconstruction. This method can be improved the speed of arithmetic operation and it has a advantage of low power consumption and small size design. The output of WDRC is converted to PDM (pulse density modulation) signal using the linear interpolation of 64 ㎑ over sample. The PDM output is not required additional DAC circuit because digital PDM is converted to analog signal through the vibration transducer which has low pass filter characteristics. And the output stage for the minimize the propagation delays is used tapered buffer strategy which consist of inverters. To verify the proposed WDRC based on the successive-FFT and PDM output, the computer simulations and experiments have been performed. For the simulation, the Matlab (Mathworks Inc., USA) is used for frequency analysis, channel gain control and signal reconstruction. Also, an FPGA development board for the verification of performance is designed by ISE 14.7 (Xilinx, USA) and Modelsim-PE 10.3 (Mentor Graphics, USA) is used for simulation of verilog-HDL algorithm. The communication data for wireless fitting is composed of 1 packet to 6 byte. The wireless communication algorithm is designed by ISE 14.7 and two modules which are TMS37157 (Texas instrument, USA) and nRF24L01 (Nordic semiconductor, Norway) can be selected for fitting. Through the in vitro fitting device, the fitting parameter is transmitted to F-IMEHD system and ACK (acknowledge character) that is same data is retransmitted to fitting device. And the total volume regardless of the channel can be controlled to 5 stage. To verify the performance of the proposed processor, the computer simulation is implemented. According to the simulation results, the designed SAR ADC can be sampled input signal and it converted to 16 bit digital data with only 1 bit error rate. And successive-FFT based WDRD can be divided into 4 channel, controlled channel gain and reconstructed input signal under the Matlab environment and FPGA development board. Also, the proposed processor had 0.13 ㎽ power consumption at 1.8 V using the Cadence simulator. Through the computer simulation and experimental results, it is verified that the proposed processor successfully worked with input signal sample, digital data conversion, channel division and reconstruction of input signal. Therefore, it is expected that the proposed processor can be applied for implementation of ASIC chip and improved the performance of F-IMEHD system.

수액 소진 알람시스템을 위한 광센서의 연구 및 제작

박효순 경북대학교 대학원 2015 국내석사

Intravenous (IV) infusion set is one of the most common treatment methods applied to hospitalized patients. However, it is necessary to check the injection of IV solution in order to prevent patients from any possible medical injury. In this paper, using the optical sensors to detect exhaustion of IV solution was proposed. The optical sensor consists of LED and photodiode that were installed on the coplanar by letting light pass using reflector and achromatic lens. The coplanar location of two elements enables to detect IV solution at the desired point conveniently. The optimum LED was selected by experiment for various wavelength of LED(R.G.B) and photodiode was located according to the lens focal distance. The suggested optical sensor can detect exhaustion of IV solution by the differences in the amount of light which was caused by properties such as total reflection, refractive index and scattering. From the implementation, the detection was available with both containers of IV solution, glass bottle and plastic pack. And also there were apparent differences in outputs by presence or absence of IV solution when the solution colors and illumination were changed, enabling to verify the practicality.

이식형 보청기용 50 ㎼급 SAR형 ADC의 설계 및 집적회로 구현

김종훈 경북대학교 대학원 2014 국내석사

Recently, Fully implantable hearing aids have been developed to compensate the problems of conventional hearing aids. The Fully implantable hearing aid consist of microphone, signal processing device, transducer. ADC is the first step of the signal processing to convert input analog signal into digital signal suitable for signal processing. In addition, low power consumption and small size of the system device are required for the convenience of implant and long-time operation after recharging because of permanently implant in the body. So, the conversion method was selected as the SAR ADC that meets the small area and low power consumption, and SAR ADC was designed considering the human speech region. In this paper, we proposed 16 bit 32 ㎑ SAR ADC for fully implantable hearing aid. As the design method of proposed SAR ADC, non-linearity problems of the sample and hold is minimized by using a dummy switch and CMOS switch, and 16 bit conversion is performed before the occurrence of LSB error. Low-power and small-area are achieved by DAC based on R-2R resistor array and comparator using power control switch and offset rejection techniques. As a result of simulation, the digital code compared with sampled input signal and output of the DAC circuit is confirmed by results. The SAR ADC is implemented in a SMIC 180 ㎚ CMOS technology. and total power consumption is 50 ㎼ under 1.8 V supply voltage and the core of SAR ADC occupies 101.315 ㎛ × 133.93 ㎛. The test result of implemented ADC chip operation showed a good performance. 최근 고령화에 따른 노인 인구 증가와 IT기술의 발달에 따른 휴대용기기의 이어폰 사용 증가 등으로 인해 다양한 연령층에서 난청 인구가 증가하는 추세이다. 난청으로 인한 의사소통의 어려움은 사회성 발달과 학습장애 등의 문제를 야기하므로[1] 보청기의 필요성이 점차 증가하고 있다. 그러나 기존의 보청기가 가지는 외관상 노출 및 착용의 불편함 등의 문제점으로 인하여 실질적인 보청기 착용 인구는 많지 않다[2,3]. 따라서 이러한 문제점을 해결하기 위해 이식형 보청기(implantable hearing aid)의 개발이 활발하게 이루어지고 있으며[4,5], 최근 완전 이식형 보청기(fully implantable hearing aid)가 더욱 주목받고 있다[6]. 완전 이식형 보청기는 1회 충전에 따른 동작 시간이 길면 길 수록 유리하며, 이식의 편의를 위해서 보청기의 크기가 작을수록 좋다. 따라서 완전 이식형 보청기의 저전력화와 소형화에 대한 연구가 더욱 중요하다. 완전 이식형 보청기는 체외 음성 신호를 전기적인 신호로 변환하는 이식형 마이크로폰(implantable microphone), 난청자의 청력 역치(hearing threshold)에 맞게 이득을 조절하는 신호 처리 장치, 그리고 진동 또는 전기 형태로 나타나는 출력장치로 구성된다. 여기서 신호 처리 장치는 다시 아날로그-디지털 변환기(analog-to-digital converter, ADC), 디지털 코어(digital core), 디지털-아날로그 변환기(digital-to- analog converter, DAC)로 구성된다. 신호 처리 장치 중, ADC는 마이크로폰에서 포집된 아날로그 형태의 음성신호를 양자화(quantization)하여 디지털 신호로 변환해 주는 것으로서, 현재까지 알려진 ADC의 대표적인 구조로는 고속의 변환에 장점을 가지는 파이프라인(pipeline) 구조와 플래시(flash) 구조, 오버샘플링(oversampling)과 노이즈 쉐이핑(noise shaping)을 기반으로 하여 높은 신호 대 잡음비의 구현이 가능한 델타-시그마(Δ-Σ) 구조, 그리고 내부 회로를 재사용함으로써 회로가 간단하게 구현할 수 있는 SAR(successive approximation register) 구조가 있다[7-9]. 이와 같이 ADC는 그 구조마다 각기 다른 특징을 가지고 있기 때문에 완전 이식형 보청기의 구현을 위하여 소형화와 저전력화에 유리한 ADC의 선정이 필요하다. 본 논문에서는 완전 이식형 보청기에 적합한 ADC를 선정하기 위해 앞서 언급한 ADC 구조들을 비교하였다. 이 과정에서 특히, 디지털 보청기 및 오디오용 ADC로 사용되는 델타-시그마 구조는 모듈레이터의 차수 및 오버샘플링율(oversampling rate)이 높을수록 회로가 복잡해지고 전력을 많이 소비하므로 사용을 배제하였고, 최종적으로 샘플 앤 홀드(sample and hold), 비교기(comparator), DAC, SAR logic의 4부분으로 구성되는 SAR 구조를 선택하였다. 그리고 음성 주파수 대역에 맞게 32 ㎑의 표본화 주파수(sampling frequency)와 16비트의 해상도(resolution)로 결정하였으며, 칩의 면적과 전력 소모를 고려하여 설계하였다. 이 과정에서, 샘플 앤 홀드 회로의 스위칭 시 통상적으로 발생되는 비선형성에 문제를 최하위 비트 오차가 발생하기 전에 변환을 수행하여 해결하였다. 그리고 R-2R 사다리형 구조(R-2R ladder type)를 가지는 DAC를 설계하여 소형화 하였다. 또한, 비교기 부분에 전력 제어 스위치를 두어 변환 시간에만 비교기가 동작하도록 함으로써 저전력 동작이 가능하게 하였다. 이와 같이 완전 이식형 보청기용 SAR ADC를 180 ㎚ CMOS 공정에 맞추어 설계하고, 컴퓨터 시뮬레이션과 측정 실험을 통해 설계한 ADC의 성능을 검토하였다.

고온스트레스 환경에서 옥수수입자도와 식물성오일 급여가 육성돈 영양소 이용성에 미치는 영향

윤원 충북대학교 2018 국내석사

The thermal environment is the most important ecological factor determining the growth, development, and productivity of domestic animals. In modern, environmental-caused heat stress is with major concern because of its harmful impacts, especially for high-productive animals. Especially, swine are extremely weak to high environmental temperatures because their sweat gland are not developed on body. When pigs are exposed to high environmental temperature and feel the heat stress, it causes various changes in the body such as blood flow, hormone, digestive system. The intestine is highly sensitive to heat stress in swine. Therefore, heat stress is directly related to pig production. Particle size of the feed ingredients is also an important factor in pig production. Thus, it is also important to find the appropriate particle size of feed ingredients at high environmental temperatures. The effects of corn particle size on nutrient digestibility and energy utilization in pigs were determined under optimal (Experiment 1: 25 ± 1 °C) or heat (Experiment 2: 37 ± 1 °C) stress conditions. In Exp. 1 and 2, five experimental diets were tested using a 5 x 5 Latin square design involving 5 barrows (Landrace × Yorkshire × Duroc, average initial body weight of 30 ± 1kg and 45.0 ± 1.8 kg, respectively in individual metabolic cages). Dietary treatments were as follows: 200, 300, 400, 600, 800 μm corn particle size obtained by mesh screens. Under optimal conditions, digestibility of dry matter (DM) and crude fiber (CF) from 200 μm diet were higher (P < 0.05) than with 300 μm and 400 μm diets. The digestibility of crude protein (CP) and ether extract (EE) were the highest (P < 0.05) at the 200 μm particle size. Digestible energy (DE) and metabolizable energy (ME) were significantly high (P < 0.05) on the 200 μm diet. Under heat stress, digestibility of CF when corn was ground to 600 μm was higher (P < 0.05) compared to 300 and 400 μm. Digestibility of NDF and ADF when corn was ground to 600 μm was the highest (P < 0.05) treatments. In conclusion, grinding corn to 200 μm corn particles maximized had a positive effect on DM, CP, EE, CF, DE ME under optimal condition, while the 600 μm corn particle size had positive effects on digestibility of CF, NDF and ADF than 200 μm corn particle size under heat stress condition. The objective of this study was to determine the effect of dietary oils on nutrient digestibility and energy utilization in pigs under heat stress (37 ± 2 °C) condition. Four experimental diets were tested using a 4 x 4 Latin square design using five barrows (Landrace × Yorkshire × Duroc, average initial body weight of 30 ± 1 kg) in individual metabolic cages per group. Dietary treatments were arranged in a 2 × 2 factorial design with two levels of oils (3.29% or 5.29%) and two types of dietary oils (Canola oil and Soybean oil). Under optimal conditions, apparent total tract digestibility (ATTD) of dry matter (DM), crude protein (CP), ether extract (EE), digestible energy (DE), and metabolizable energy (ME) were not significantly different among treatments. Average daily gain (ADG), average daily feed intake (ADFI), and feed efficiency were not significantly different among treatments either. However, significant (p < 0.05) effects on DE and ME values were found among groups.

그래핀-PMMA 진동막을 적용한 고감도 고막 설치형 마이크로폰

우승탁 경북대학교 대학원 2016 국내박사

Fully implantable hearing devices (FIHDs) have been developed to overcome the problems of existing air-conductive hearing aids, and two models have been used commonly so far. The microphone is an important input component that can affect the overall performance of FIHDs. Therefore, vigorous research on implantable microphones has been carried out. In particular, the microphone of FIHDs needs to have an excellent frequency response in the auditory range and must be easy to implant, insensitive to external vibration noise, and miniaturized. Typically, the FIHD microphone is implanted under the skin near the temporal bone or inside the middle ear. However, these types of implantation make it hard to improve the performance of the FIHDs. In particular, in the case of the microphone of FIHDs implanted under the skin, because of the filtering effect of the skin, severe degradation of the microphone sensitivity is unavoidable in high-frequency regions and the pickup problem of noise occurs during mastication. In the case a piezoelectric microphone implanted in the middle ear, a considerably flat frequency response is shown. However, its implantation requires invasive surgery and the ossicles must be dislocated in part to prevent feedback signals caused by the actuator that is located on the same path. Another type of microphone is based on a capacitive acceleration sensor that collects sounds by using the movement of the tympanic membrane. However, it has a low sensitivity of less than 0.8 kHz due to the acceleration characteristics of the sensor. Thus, new implantable microphone designs that can overcome the problems of existing microphones are needed. In this paper, we propose a trans-tympanic microphone with a high-performance diaphragm made of graphene–polymethylmethacrylate (PMMA) and with high displacement up to the 7 kHz region in the auditory range. The proposed microphone is placed at the pars tensa of the tympanic membrane. Thus, it has the advantage of using the auditory path (i.e., the pinna, the ear canal). Additionally, the trans-tympanic microphone is easy to implant with the use of ventilation tube technology, which is normally used in otorhinolaryngologic surgery for otitis media. However, the diameter of the microphone diaphragm must be limited to below 4 mm because of the anatomy of the tympanic membrane, making it difficult to obtain excellent sensitivity. Typically, diaphragm of an electret condenser microphone (ECM) is fabricated with polyphenylenesulfide (PPS) affiliated with based polymer because of the low cost and high efficiency of mass production. The commercial ECM with a diaphragm of 4 mm in diameter has an effective diameter of 2.65 mm and an elastic modulus of 2.0–3.3 GPa and a thickness of 3.6 μm. Therefore, it has a resonant frequency of 7–10 kHz, and its displacement is 30–40 nm. However, the microphone capacitance change between diaphragm and back plate is limited due to this displacement, so the sensitivity of the microphone is –30 to 35 dB (0 dB = 1V/Pa). A hearing aid with an excellent dynamic range should have a microphone with high sensitivity and a small minimum detection level. Thus, diaphragm for the trans-tympanic microphone with large displacement according to the sound pressure in auditory range needs to be designed. By using the stacked structure of the PMMA with low density and a low elastic modulus and graphene with a high elastic modulus, it is designed to have high displacement up to the 7 kHz region in the auditory range. The graphene–PMMA diaphragm is designed to have a relatively low elastic modulus and low density compared with a commercial ECM diaphragm of the same size, thereby giving it high displacement and a resonant frequency close to 7 kHz. The high displacement of the diaphragm gives it very high sensitivity, thereby giving the trans-tympanic microphone wide dynamic range. For the design of the graphene–PMMA structure diaphragm, the elastic modulus of the diaphragm according to the thickness ratio of the stacked structure was measured using the indentation system. Then, the density of the stacked structure, which is a combination of different densities, was calculated. Using the measured properties and mathematical analysis of the diaphragm, the resonant frequency and displacement were predicted and the optimal ratio of graphene–PMMA was deducted. We used a laser Doppler vibrometer to evaluate the fabricated diaphragm, which had an effective diameter of 2.65 mm and a thickness of 3.6 μm, and found that it had a high displacement of 6.8dB up to the 7 kHz region compared with that of a commercial ECM diaphragm of the same size. We also fabricated a trans-tympanic microphone package of 4 mm in diameter and 3.2 mm in height incorporated with the graphene–PMMA diaphragm. We evaluated the quality of the frequency responses and the total harmonic distortion of the microphone and found that it had an excellent sensitivity of –20 dB up to the 7 kHz region, which is, on average, 9dB higher than that of a microphone with a commercial ECM diaphragm. Finally, we conducted experiments using a human cadaver to evaluate the usefulness of the microphone as an input device for FIHDs. The result of the experiment showed a high sensitivity of −18 dB on average in the auditory range. As a result, we demonstrated the high performance of the proposed trans-tympanic microphone. Thus, it is highly expected to be utilized practically as a microphone for FIHDs.