Search

This study aims to clarify the relationship between the layer structure transition of fibers caused by the change in the flow field and the thermal properties and fiber interaction when the glass fiber content is changed. Polyamide 6 samples with different short glass fiber contents were prepared, and changes in layer structure during the flow process of injection molding were compared using X-ray computed tomography. An injection-molding simulation was performed to compare the changes in the layer structure of fibers during the flow process, and the temperature distribution and shear rate distribution were obtained by numerical analysis. Furthermore, the effect of fiber interaction on the layer structure transition of fibers was considered using a relaxation function composed of the fiber content, fiber shape factor, and strain rate.

Electrically conductive nano-fillers, such as carbon nanotubes (CNT), carbon black (CB) and carbon fibers (CF), have been of great interest to polymer scientists because their reinforcement into polymer matrices gives rise to conductive thermoplastics. However, it is found that their orientation distributions after the injection molding process reduce the interparticle contacts between particles and thus decreases the electrical conductivity. In this study, it is shown that electrically conductive networks can be re-tailored through post-processing annealing at a temperature higher than the glass-rubber transition temperature of the polymer. We demonstrate these results for polycarbonate (PC) composites produced by injection molding using different fillers including single-walled CNT (SWCNT), multi-walled CNT (MWCNT), CB and CF. The annealing-induced increase in the electrical network path is proved by electrical conductivity improvement. It can be explained by a transition from aligned, unconnected particles before annealing to an interconnected network after annealing through the viscoelastic relaxation of the polymer. Compared with CB- and CF-based PC composites, CNT-based PC composites at low contents exhibited outstanding conductivity improvement after isothermal annealing for several minutes. Moreover, the CNT network helps to keep the composite shape and strength after annealing. Especially, SWCNT nanocomposites have potential to rapid the tailoring process of the electrical network without significant size extension and strength reduction. The post-processing annealing may exploit the future applications of injection-molded CNT polymer composites.

This study investigates the causal relationship between Income Inequality and Healthcare Expenditure within a quantile panel-type causality framework using yearly panel data from 2004 to 2017. The empirical results show that within the high-growth regime of health expenditure to income ratio, reducing the deterioration of income inequality can make the ratio of health expenditure to income keep increasing. Besides, within the extreme income inequality regime, the ratio of health expenditure to income continues to increase, which can reduce the deterioration degree of income inequality. This paper presents evidence that to improve the continuous deterioration of income inequality; it should focus on the continuous increase in the ratio of health expenditure to income, not just the continuous increase in health expenditure. Accordingly, policy-makers should be cautious about the momentum between the ratio of health expenditure to income and income inequality when they reach the extremely quantiles.

To realize the potential applications of carbon nanotube (CNT) polymer composites produced using injection molding, the CNT networks in composite parts need to be tailored and controlled by processing conditions. In this study, microinjection-molded polycarbonate matrix composite filled with multi-walled carbon nanotubes were prepared from twin-crew extruded pellets using plate-shaped double-cavity. The CNT electrical network in these microinjection-molded parts was observed directly in both cross-section and longitudinal-section using the lock-in thermography technique (LIT). The results showed the skin/shell-core structure with the high degree of inter-connected CNT in the core region, the inhomogeneous conductivity along the injection direction and the lower conductivity near the gate. This is confirmed by inspecting the scanning electron microscopy and polarized Raman mapping images. The effect of total injection molding time, mold temperature and melt temperature on the electrical network and conductivity were also investigated. The observed conductivity variations were explained in term of the processing conditions that induced the CNT network structures in the skin and core regions.

In this study, adding carbon nanotubes (CNTs) to poly (ether ether ketone) (PEEK) not only improved the mechanical properties, but also improved the thermal resistivity of PEEK owing to the CNTs’ function as an antioxidant. The PEEK–CNT composite did not show large weight loss at 450 °C. The stabilization energies (ΔG) of CNTs for 1,4-diphenoxybenzene radical and 4-phenoxyphenol radical, which are decomposition products of PEEK at 450 °C, were calculated by density functional theory, and they were estimated to be −80.3 and 150.2 kJ mol−1, respectively. It was confirmed that 1,4-diphenoxybenzene radical could be trapped in a high-temperature environment of 450 °C by the CNTs. The addition of CNTs yielded almost no change in formability, but the mechanical properties such as tensile strength and bending strength were greatly improved. The PEEK–CNT composite is expected to have improved heat resistivity and mechanical properties, as well as higher reliability, so that it can be used in the future in various fields such as aerospace and automotive.

This study investigates the correlation between the fiber orientation distribution along the thickness and mechanical anisotropy in injection-molded products using a thermoplastic resin reinforced by short fibers. To this end, polyamide-6 samples containing 15, 30, 50, and 65 wt% of short fiberglass were compounded, and flat plates with side gates were injection-molded. The fiber orientation distribution near the center of the plates was observed via X-ray computed tomography and that along the thickness was quantified via a fiber orientation tensor. Coupon test pieces were cut from the plates along the machine and transverse directions, and a three-point bending test was performed. Mechanical anisotropy was evaluated from the ratio of the flexural modulus in each direction. Evaluation results of the fiber orientation distribution and mechanical anisotropy were compared. As a result of the above investigation, a clear correlation was found between the fiber orientation distribution and mechanical anisotropy when the glass fiber content was 15–50 wt%. In the anisotropic expression under the condition of high glass fiber content (65 wt%), contributions of parameters other than the fiber orientation distribution became evident.

TÓM TẮT Đặt vấn đề: Nhiễm khuẩn sơ sinh sớm là một trong những nguyên nhân gây tử vong cao ở giai đoạn sơ sinh nhưng việc chẩn đoán sớm còn gặp nhiều khó khăn. Vì thế, chúng tôi tiến hành nghiên cứu này nhằm mục đích tìm hiểu các yếu tố nguy cơ giúp thiết lập chẩn đoán nhiễm khuẩn sơ sinh sớm. Đối tượng, phương pháp: Nghiên cứu hồi cứu. Lấy mẫu toàn bộ gồm 295 trẻ sơ sinh được chẩn đoán nghi ngờ nhiễm khuẩn sơ sinh sớm trong 72 giờ đầu sau sinh. Sau đó, chia thành hai nhóm: nhóm nhiễm khuẩn (các trường hợp nhiễm khuẩn hay có khả năng nhiễm khuẩn) và nhóm không nhiễm khuẩn để so sánh. Địa điểm nghiên cứu: phòng Nhi sơ sinh, Bệnh viện Trường Đại học Y Dược Huế từ tháng 5/2019 đến tháng 5/2020. Kết quả: Tỷ lệ của nhóm nhiễm khuẩn là 57,3%. Các yếu tố liên quan giúp chẩn đoán nhiễm khuẩn sơ sinh sớm bao gồm: ối vỡ non (OR = 4,7), thời gian ối vỡ trên 18 giờ (OR = 2,5), da tái, nổi vân tím (OR = 14,9), trẻ có chỉ định thở máy (OR = 8,7), suy hô hấp bắt đầu sau 4 giờ tuổi (OR = 6,8), kém linh hoạt (OR = 6,6), bụng chướng (OR = 4,2), thở nhanh (OR = 2,7), nôn (OR = 2,3), số lượng bạch cầu trong máu ngoại vi > 25 x 109/L (OR = 5,7), tỷ lệ bạch cầu đa nhân trung tính > 65% (OR = 2,0) và nồng độ CRP huyết thanh > 10 mg/L (OR = 8,0). Kết luận: Việc phối hợp các yếu tố nguy cơ trong thai kỳ, triệu chứng lâm sàng và cận lâm sàng, giúp xác định chẩn đoán nhiễm khuẩn sơ sinh sớm, nhằm hạn chế tối đa việc sử dụng kháng sinh không cần thiết ở trẻ sơ sinh. Từ khóa: Sơ sinh, nhiễm khuẩn sơ sinh sớm, yếu tố nguy cơ trước sinh ABSTRACT RELATED FACTORS OF EARLY-ONSET NEONATAL INFECTION AT HUE UNIVERSITY OF MEDICINE AND PHARMARCY HOSPITAL Background: Early - onset neonatal infection is an important cause of morbidity and mortality in neonates and it’s diagnosis remains challenging. Therefore, this study aimed to describle the related factors that can help establish the diagnosis of early - onset neonatal infection. Methods: A retrospective study. A total sample of 295 neonates at Hue University of Medicine and Pharmacy Hospital, Hue, Viet Nam from 5/2019 - 5/2020, who were suspected to suffer from infection within the first 72 hours of life. Then, they were classified as infected group (confirmed or possible infected) and non - infected group to compare. Results: The prevalence of infected group is 57,3%. Some related factors of early - onset neonatal infection are: prelabour rupture of membranes (OR=4,7), rupture of membranes for more than 18 hours (OR = 2,5), pale or mottled skin (OR = 14,9), need for mechanical ventilation (OR = 8,7), respiratory distress starting more than 4 hours after birth (OR = 6,8), responsiveness (OR = 6,6), abdominal distension (OR = 4,2), tachypnoea (OR = 2,7),vomiting (OR = 2,3), white blood cell in peripheral circulation > 25 x 109/L (OR = 5,7), neutrophil ratio in peripheral circulation > 65% (OR = 2,0) and CRP concentrations > 10 mg/L (OR = 8,0). Conclusions: Combination of perinatal risk factors, clinical and subclinical characteristcs are highly suggestive for early - onset neonatal infection will help to reduce the numbers of babies given antibiotics unnecessarily. Key words: Neonate, early - onset infection, perinatal risk factors

In this study, short-glass-fiber-reinforced poly(butylene terephtalate) with embossed decorative patterns was produced by an injection molding using a plated-shape cavity with embossed fine convexo-concave patterns on a fixed one-sided surface. The influence of the molding conditions, the fiber contents, and the fiber orientation distributions on the embossed-surface quality of the injection-molded parts was investigated by experiment methods. A method for evaluating the quality of the embossed surface using a spectrum analysis computes Fourier transform from surface roughness data was presented. Further, the software CIMP-PACK3DM was employed to analyze the resin flow in the specimens using the finite element method. The numerical results were in good quantitative agreement with the experimental methods. Consequently, the study aimed to find out an approach for produce a favorable surface quality from considering the resin surface temperature and resin pressure in the filling process, or the fiber orientation prediction of final part.

Being able to measure the fiber orientation distribution in the injection-molded composite parts is of considerable importance, since the distribution locally affects the mechanical and physical properties of the final part such as its strength, impact toughness, internal stress, and fatigue properties. In this study, we experimentally measured the fiber orientations in two injection-molded specimens produced from 30 wt% short-glass-fiber-reinforced polyamide 6 using plate-shaped cavities with and without a weld-line. The fiber orientation distributions were observed directly using a high-resolution three-dimensional (3D) X-ray computed tomography (CT) system XVA-160α. A simple method based on a series of X-ray CT images was developed to measure the orientation angles of the individual fibers. Further, precise 3D calculations of the fiber orientations related to the second-order orientation tensor components were performed to obtain a consistent description of the observed behavior. Consequently, this study explored a potential application of X-ray CT imaging, a novel and powerful technique for observing and measuring fiber orientation. Further, the software CIMP-PACK3DM was employed to analyze the resin flow in the mold cavity using the finite element method (FEM). The filling patterns of the injection-molded plates with and without a weld-line as determined using FEM were in good quantitative agreement with the X-ray CT imaging analysis results. It was found that the fiber 3D orientation distributions of the injection-molded plates with and without a weld-line could be obtained with precision by combining the high-resolution 3D X-ray CT system XVA-160α with the resin flow analysis software CIMP-PACK3DM using FEM.

Properties of fiber-reinforced composite are dominated by the microstructure of the fabricated part rather than the properties of constituent materials. As the microstructure of composite is related to the flow-processing route of the fiber-reinforced suspensions and the geometry of the mold, the microstructure of composite can be tailored in order to achieving high-performance composites by exercising control over the flow processing. Thus, numerical methods are used to model the resin flow, the fiber orientation, and mold design, and they become important challenges during molding process. In our previous research, a theoretical fiber-fiber interaction model with a global fiber interaction coefficient was developed. In this study, the three-dimensional (3D) fiber orientation distribution is predicted by combining our developed fiber interaction model and improved Anisotropic Rotary Diffusion - Retarding Principle Rate (iARD-RPR) model. The fiber orientation calculation started from the gate, and from a ...

Many economists believe that China avoided the so-called Asian flu due to its strong balance of payments position and substantial foreign reserves. This study introduces an improved method for testing financial-crisis contagion and shows that crisis-contagion effects were significant among Thailand and the Chinese economic area (i.e. China, Hong Kong, and Taiwan) stock markets during the Asian financial crisis. The main contribution of this study is its use of a two-step procedure to identify the crisis dates for testing for contagion and data pertaining to a growing triangular economic area during the Asian financial crisis. This result suggests that if investors ignore the economic and financial information within regional markets, they will face an increase in uncertainty vis-a-vis investment returns.

This study examines the short-run and long-run inflation hedging effectiveness of gold in the United States and Japan during the period of January 1971 to January 2010. Previous research has shown in the long-run that inflation tends to appropriately increase the price of gold in the U.S., leading to gold's popularity as an asset in portfolios to reduce the risk against sudden inflation. However, gold is only partially effective in hedging against inflation in Japan. This research found that the rigidity between the price of gold and the consumer price index affects the inflation hedging ability of gold in the long-run. The gold price is characterized by market disequilibrium induced by the price rigidity, causing the price of gold to be unable to response to changes in the CPI. To explore the inflation hedging ability of gold in the short-run, this study further examines the price rigidity in low and high momentum regime. It is found during the low momentum regimes that, gold return is unable to hedge against inflation in either the U.S. or Japan. However, during high momentum regimes, gold return is able to hedge against inflation in the U.S., while the price rigidity in Japan causes the price of gold to not fully hedge against inflation in the short-run.

The theoretical fiber-interaction model for calculating the fiber orientation in the injection molded short fiber/thermoplastic composite parts was proposed. The proposed model included the fiber dynamics simulation in order to obtain an equation of the global interaction coefficient and accurate estimate of the fiber interacts at all orientation states. The steps to derive the equation for this coefficient in short fiber suspension as a function of the fiber aspect ratio, volume fraction and general shear rate are delineated. Simultaneously, the high-resolution 3D X-ray computed tomography system XVA-160α was used to observe fiber distribution of short-glass-fiber-reinforced polyamide specimens using different cavity geometries. The fiber orientation tensor components are then calculated. Experimental orientation measurements of short-glass-fiber-reinforced polyamide is used to check the ability of present theory for predicting orientation. The experiments and predictions show a quantitative agreement and confirm the basic understanding of fiber orientation in injection-molded composites.

This article is an attempt to test, through the use of forward forecasting test on dynamic conditional correlation (DCC), for contagion between Taiwan and US stocks under asymmetry. The process includes three steps. The first step uses the iterated cumulative sums of squares (ICSS) algorithm to detect the structural breaks of market return. The second step creates dummy variables for breaks, estimates EGARCH model of conditional generalized error distribution, and computes dynamic conditional correlation coefficients of DCC multivariate GARCH model. The third step employs one-step and N -step forecast test to check for contagion effect. The evidences prove the asymmetric leverage effect of Taiwan weighted stock index and New York—NYSE Composite Index. Interestingly, we discovered that there are two kinds of contagion, “positive” and “negative”, between markets.

Numerical prediction of the fiber orientation in the short-glass fiber (GF) reinforced polyamide 6 (PA6) composites with the fiber weight concentration of 30%, 50%, and 70% manufactured by the injection molding process is presented. And the fiber orientation was also directly observed and measured through X-ray computed tomography. During the injection molding process of the short-fiber/thermoplastic composite, the fiber orientation is produced by the flow states and the fiber-fiber interaction. Folgar and Tucker equation is the well known for modeling the fiber orientation in a concentrated suspension. They included into Jeffrey’s equation a diffusive type of term by introducing a phenomenological coefficient to account for the fiber-fiber interaction. Our developed model for the fiber-fiber interaction was proposed by modifying the rotary diffusion term of the Folgar-Tucker equation. This model was presented in a conference paper of the 29th International Conference of the Polymer Processing Society published by AIP conference proceeding. For modeling fiber interaction, the fiber dynamic simulation was introduced in order to obtain a global fiber interaction coefficient, which is sum function of the fiber concentration, aspect ratio, and angular velocity. The fiber orientation is predicted by using the proposed fiber interaction model incorporated into a computer aided engineering simulation package C-Mold. An experimental program has been carried out in which the fiber orientation distribution has been measured in 100 x 100 x 2 mm injection-molded plate and 100 x 80 x 2 mm injection-molded weld by analyzed with a high resolution 3D X-ray computed tomography system XVA-160α, and calculated by X-ray computed tomography imaging. The numerical prediction shows a good agreement with experimental validation. And the complex fiber orientation in the injection-molded weld was investigated.

This study creates the threshold vector autoregression model and employs quarterly data of Taiwan from 1981 to 2006 to examine the relationship between foreign direct investment (FDI) and domestic gross direct investment (GDI). Our framework provides a consideration of business cycle asymmetry that quite differs from the existing approach. We find that (1) the long-run relationship between FDI and GDI is complementary; (2) the relationship between FDI and GDI is substitutive during expansion, however, is complementary during recession; (3) a depreciation of the Taiwanese Dollar helps attract FDI during expansion, but decrease GDI during recession; (4) the negative impact of Taiwan's outward foreign direct investment and national saving on GDI, the negative impact of GDP on GDI and the negative impact of Taiwan's outward investment on FDI are only evident during recession; and (5) macroeconomic variables indirectly affect FDI during expansion and GDI during recession through the adjusting process toward equilibrium.