A Novel Injectable pH–Temperature Sensitive Hydrogel Containing Chitosan–Insulin Electrosprayed Nanosphere Composite for an Insulin Delivery System in Type I Diabetes Treatment

Thuy An Trinh,Thai Minh Duy Le,Hoang Gia Vinh Ho,Thi Cam Thach To,Vu Viet Linh Nguyen,Dai Phu Huynh,Doo Sung Lee 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.1

Faculty of Materials Technology, Ho Chi Minh University of Technology (HCMUT)/Vietnam National University Ho Chi Minh City; ¹School of Chemical Engineering and Theragnostic Macromolecules Research Center, Sungkyunkwan University; ²Vietnam National University Ho Chi Minh City/National Key Laboratory of Polymer and Composite Materials, Ho Chi Minh University of Technology, Vietnam National University; ³Faculty of Materials Technology, Ho Chi Minh University of Technology (HCMUT)/ Vietnam National University Ho Chi Minh City/Research Center for Polymeric Materials, Ho Chi Minh University of Technology, Vietnam National University In this research, a novel insulin composite delivery system was prepared and characterized. Insulin drug was loading in chitoshan nanospheres using electrospraying method, a pH- and temperature-sensitive biodegradable hydrogel, which is an oligomer serine-poly(lactide)-poly(ethylene glycol)-poly (lactide)-oligomer serine (OS-PLA-PEG-PLA-OS) pentablock copolymer was used as a matrix to containing chitosan–insulin electro sprayed nanospheres (CIN). The properties of the OS-PLA-PEG-PLA-OS pentablock copolymer and the chitosan–insulin nanoparticles such as sol-gel transition, degradation in vitro and in vivo were characterized. The results showed that the chitosan–insulin nanospheres uniformly distributed in the matrix had a reinforcing effect on the mechanical properties and prolonged the degradation time of the hydrogel depot under body conditions. In addition, the cytotoxicity experiment results indicate that the composite could be used as a biomaterial for drug delivery system. The composite solutions accommodating different concentrations of the chitosan–insulin nanospheres were subcutaneously injected into induced diabetic BALB/c mice to study the in vivo insulin-release profile. The result showed that insulin concentrations in blood plasma were maintained at a steady-state level. Furthermore, the bio-properties of the insulin were retained and it showed a blood glucose level reducing effect for more than 60 hours after injection to a streptozotocin (STZ)-induced diabetic mouse model. The results suggested that this injectable pH–temperature sensitive hydrogel containing chitosan– insulin electro sprayed nanosphere composites has promising potential applications for type 1 diabetes treatment.

Modelling and experimental validation for off-design performance of the helical heat exchanger with LMTD correction taken into account

Nguyen Minh Phu,Nguyen Thi Minh Trinh 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.7

Today the helical coil heat exchanger is being employed widely due to its dominant advantages. In this study, a mathematical model was established to predict off-design works of the helical heat exchanger. The model was based on the LMTD and e-NTU methods, where a LMTD correction factor was taken into account to increase accuracy. An experimental apparatus was set-up to validate the model. Results showed that errors of thermal duty, outlet hot fluid temperature, outlet cold fluid temperature, shell-side pressure drop, and tube-side pressure drop were respectively ±5%, ±1%, ±1%, ±5% and ±2%. Diagrams of dimensionless operating parameters and a regression function were also presented as design-maps, a fast calculator for usage in design and operation of the exchanger. The study is expected to be a good tool to estimate off-design conditions of the single-phase helical heat exchangers.

Characteristics of pressure and force considering friction in a closed cylinder with a holed piston

Nguyen Minh Phu,이근식 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.6

A mathematical model for a closed cylinder with a holed piston was established to investigate the operational characteristics of a gasspring. An ideal gas working fluid and an adiabatic process were assumed in the model. Simulation and experimental results for a typicaldesign and operational condition showed good agreement. The model was then used to investigate the effects of the orifice diameter, thefilling pressure, and the velocity of the piston on the applied force and operating pressures of two chambers in the gas spring. The resultsshowed that the orifice diameter and the piston velocity had significant effects on the pressure difference between the two chambers. A0.05-mm reduction in the orifice diameter led to an approximately two-fold increase in the pressure difference. A 10% increase in thepiston velocity resulted in an approximately 25% increase in the pressure difference. The orifice diameter and the piston velocity had agreater effect on the chamber with lower pressure than on the chamber with higher pressure. The force applied to the piston also variedwith the piston velocity, the orifice diameter, and the filling pressure due to irreversibilities including the throttling process through theorifice and friction between the wall and the piston. The present model and results are expected to supply useful information about a newgas spring design.

A Magnetization Study of Prussian-blue Analogue Na<SUB>x</SUB>Mn<SUB>y</SUB>[Fe(CN)₆]

Nguyen Van Minh,Phung Kim Phu,Nguyen Minh Thuan,Duong Manh Toan,In-Sang Yang 한국자기학회 2008 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Augmented heat transfer and friction investigations in solar air heater artificially roughened with metal shavings

Nguyen Minh Phu,Vo Tuyen,Tu Thien Ngo 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.7

The paper presents the effect of the Reynolds number, relative roughness height and relative roughness pitch on the heat transfer and pressure loss in a solar air heater. A novel absorber plate with metal shavings from the turning of a steel shaft is employed to reduce the cost of production and to be available for the manufacturing industry. The parameters studied ranged from 5000 to 25000 for the Reynolds number, from 4.7 to 9.4 for the relative roughness pitch (P/e) and from 0.26 to 0.43 for the relative roughness height (e/D h ). The results show that there are some characteristics that differ from the published studies. The optimum e/D h is 0.35 to obtain the highest thermo-hydraulic performance parameter, and the parameter increases with a decrease in P/e. Within the scope of the study, the maximum thermo-hydraulic performance parameter is approximately 1.5. The correlations between the Nusselt number and the friction factor are developed based on the experimental data. The results from the correlations and from the experimental data are fairly in agreement.

A Magnetization Study of Prussian-blue Analogue Na<SUB>x</SUB>Mn<SUB>y</SUB>[Fe(CN)<SUB>6</SUB>]

Nguyen Van Minh,Phung Kim Phu,Nguyen Minh Thuan,In-Sang Yang 한국자기학회 2008 Journal of Magnetics Vol.13 No.4

In this report, we present the results of a study on the effects of the particle size on the properties of the Prussian blue (PB) analog NaxMny[Fe(CN)?]. A novel synthesis method of the NaxMny[Fe(CN)?] nano-particles using an organic solvent, formamide, is employed. The size of the PB particles is found to be 100-150 ㎚ for the samples prepared in the formamide solvent, which is much smaller than that of the samples prepared using water only. The broadening of the X-ray diffraction peaks of the nano-sized PB samples is attributed to the lattice disorder and a dramatic reduction in the particle size. The compositions of the samples are confirmed by an energy-dispersive X-ray analysis (EDAX), and the result proves that the samples are actually NaxMny[Fe(CN)?] Prussian blue. The UV-vis spectra show a broad intervalence charge-transfer (CT) band in the visible region between 400 and 700 ㎚, and the absorption decreases abruptly in the green region for the nano-sized PB sample. A divergence between the field cooled (FC) and zero field cooled (ZFC) magnetization curves is observed for the nano-sized PB sample at 11 K, indicating that nanoparticles in the sample are single domain superparamagnets with a blocking temperature of 11 K. Our results reveal that the nano-sized PB samples show significantly different optical and magnetic properties than those of the bulk PB samples.

관 내부 냉매비등이 있는 수직관 외부 얼음 형성 연구

Nguyen Minh Phu,이근식(Geun Sik Lee) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.2

얼음 제조와 잠열 저장 등에서 수직관 내부를 저온의 냉매를 흘려, 관 외부의 물을 얼리는 과정에서 내부 냉매의 비등열저항과 외부 얼음열저항이 얼음형성에 미치는 영향에 대하여 조사되었다. 상변화 및 비등열전달 관계식들이 도입되어 얼음두께와 관련변수들이 해석되었으며, 작동유체로는 냉매 22 와 냉매 134a 가 사용되었다. 이들의 건도는 0-0.8 범위이다. 해석결과, 최초 약 30 분까지는 내부냉매의 대류저항이 얼음의 전도저항에 비하여 높으나, 그 이후 얼음의 두께 증가에 따른 얼음전도저항의 현저한 증가로 인하여 냉매에 공급되는 열플럭스가 감소되므로 냉매 측 건도와 비등 및 대류열전달계수도 현저히 감소함을 알 수 있었다. 냉매 22 는 대류열전달계수가 냉매 134a 보다 높아서 단위 면적 당 더 많은 얼음을 생성할 수 있음을 알 수 있었다. An ice-making model has been developed and analyzed in this study. The effects of the following on the ice formation on the outer surface of a tube in which a refrigerant flows and boils are numerically investigated: thermal resistance of the refrigerant and thermal resistance of the ice formed on the outer surface of the tube. The ice thickness and related variables are analyzed in the case of the refrigerants R22 and R134a by using the expressions for phase-change heat transfer and boiling heat transfer coefficient. Vapor qualities of the refrigerants range from 0 to 0.8. As a result, up to the first 30 min, the internal convection resistance is higher than the thermal resistance of the ice on the external surface of the tube. However, after about 30 min, the thermal resistance of the ice increases remarkably due to the increase in the ice thickness. Thus, the heat flux to the refrigerant decreases, and further, the refrigerant quality and the boiling heat transfer coefficient also decrease. As the heat transfer coefficient of R22 is higher than that of R134a, the mass of the ice formed when R22 is used is higher than that formed when R134a is used.

입구 물온도와 열부하가 냉각탑의 팬동력에 미치는 영향 분석

Nguyen Minh Phu,이근식(Geun Sik Lee) 대한기계학회 2013 大韓機械學會論文集B Vol.37 No.3

막충진재(film fill)를 갖는 냉각탑용 팬의 효율적인 운전조건을 제시하기 위하여, Merkel 의 이론을 바탕으로 한 종전의 최적 총연간비용 모델을 사용하여 입구 물온도와 열부하에 따른 최소팬동력을 구하는 프로그램이 새로이 개발되었으며, 냉각탑의 설계 맵이 본 연구로부터 제시되었다. 전형적인 예들을 통하여 본 프로그램의 타당성이 입증되었다. 주어진 열부하에서 이들 팬동력(z 축)-공기질량플럭 스(x 축, 최소팬동력 존재)-입구물온도(y 축, 최소팬동력의 최대값 존재)의 3 차원 그래프는 말안장 형상으로 나타났다. 최소팬동력들은 열부하에 따라 증가하였다. 따라서,‘고온수 유입과 저유량의 공기로 작동’될 때가 항상 최소팬동력 조건이 아니며, ‘주어진 입구물온도에 대하여 최소팬동력에 대응하는 최적의 공기질량플럭스가 (열부하와 무관하게) 존재한다’는 사실이 본 연구결과로부터 밝혀졌다. In order to provide effective operating conditions for the fan in a wet cooling tower with film fill, a new program to search for the minimum fan power was developed using a model of the optimal total annual cost of the tower based on Merkel’s model. In addition, a type of design map for a cooling tower was also developed. The inlet water temperature and heat load were considered as key parameters. The present program was first validated using several typical examples. The results showed that for a given heat load, a three-dimensional graph of the fan power (zaxis), mass flux of air (x-axis, minimum fan power), and inlet water temperature (y-axis, maximum of minimum fan power) showed a saddle configuration. The minimum fan power increased as the heat load increased. The conventionally known fact that the most effective cooling tower operation coincides with a high inlet water temperature and low air flow rate can be replaced by the statement that there exists an optimum mass flux of air corresponding to a minimum fan power for a given inlet water temperature, regardless of the heat load.

냉수공장에서 열전달을 고려한 응축기와 증발기의 물 압력강하 특성

Nguyen Minh Phu,이근식(Geun Sik Lee) 대한기계학회 2011 大韓機械學會論文集B Vol.35 No.12

물 냉각기의 응축기와 증발기의 형상(길이, 관 직경, 관수, 통로 수)은 설비비용에 관련된 열전달 면적과 운전비용에 관련된 압력강하와의 조화로 결정될 수 있다. 물 냉각기 (냉동사이클)의 쉘-관 형상의 열교환기(응축기와 증발기)의 관 내부로 물이 통과할 때, 주어진 냉각부하와 요구조건을 만족하면서, 물 압력강하가 작은 설계조건에 초점을 맞추었다. 상업용 강화튜브의 사용과 상용 소프트웨어를 사용한 해석결과의 검증으로 실용성과 신뢰성 확보를 도모하였다. 해석결과, 관 통로 수를 적게, 관 직경을 크게, 관 수를 많게 선정하면, 관 길이를 짧게 하므로 물측 압력강하를 줄일 수 있었다. 그러나, 관수가 특정값보다 많을 때는 오히려 작은 관 직경을 사용하는 것이, 내부열저항의 감소로 인한 단위 길이 당 총 열저항 감소 때문에, 관 길이를 짧게 하여 설비비용을 줄일 수 있었다. The configurations of the evaporator and condenser of a water chiller can be determined from the trade-off between the heat transfer area, which is related to the capital cost and the pressure drop, which is associated with the operational cost. In this study, the design of the water chiller focused on minimizing the water pressure drop of both condenser and evaporator for given cooling capacity and requirements. Commercial enhanced tubes were employed to simulate real-life conditions. The results of the present analysis were compared with those obtained by HTRI software for verifying them. The results indicated that a reduction in the water pressure drop, which is associated with the short length of a tube, can be effected by decreasing the number of tube passes and increasing the number of tubes and the tube diameter. However, using a large number of tubes with smaller diameters can reduce the capital cost because the tubes are short. The reduction of the capital cost is due to the fact that a small-diameter tube has low internal thermal resistance and hence contributes to a decrease in the overall thermal resistance per unit length.

관 내부 비등이 있는 수직관 외부 얼음 형성 연구

Nguyen Minh Phu,이근식(Geun Sik Lee) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5

얼음 제조와 잠열 저장 등에서 열전달 향상을 위하여 수직관 내부를 저온의 냉매가 흐르도록 하여, 관 외부의 물로부터 열을 흡수하여 얼음이 형성되는 현상에 대하여 해석되었다. 상변화 열전달 및 비등 열전달 관계식들이 도입되어 해석되었으며, 작동유체로는 냉매 22와 냉매 134a가 사용되었으며, 이들의 건도는 0-0.8 범위이다. 5시간 얼음제조과정을 기준으로 할 때, 최초 2 시간 이내에 형성되는 얼음의 양이 총 얼음 양의 약 45%이상을 차지하였다. 얼음의 열저항이 얼음 형성에 미치는 영향은 비등 열전달계수, 열플럭스와 건도와 같은 다른 변수들에 비하여 현저하였다. 냉매 22의 열전달 계수는 냉매 134a 의 경우보다 높다. 따라서 냉매 134a 보다 냉매 22를 사용한 경우의 얼음 두께가 두껍다. 열전달 면적에 대한 얼음 질량의 비를 살펴보면, 냉매 22의 경우가 냉매 134a 의 경우보다 높다. An ice making model has been developed and analyzed. In order to improve heat transfer, ice is frozen on the outer surface of a tube cooled directly with boiling refrigerant to flow internally. The model is based on available expressions about phase change heat transfer and boiling heat transfer coefficient. R22 and R134a were used as heat transfer fluids and their vapor qualities were in range of 0 to 0.8. The mass of ice formed within 2 hour took up nearly half of total mass of ice. The results show that influence of ice thermal resistance on other parameters such as boiling heat transfer coefficient, heat flux and quality is remarkably higher, compared with until the ice has not been formed yet. Heat transfer coefficient of R22 is higher than that of R134a. Therefore, ice thickness in case of R22 is thicker and shorter than that in R134a. The ratio of mass of ice to heat transfer area for R22 is also higher than that for R134a. The model and results can be applied to both ice making and latent thermal energy storage.