Search

Incorporating lightweight aggregate (LWA) in concrete decreases its density. The high porosity of LWA contributes to low density but also high absorption characteristics. LWA absorbs water even in ...

Polyampholyte (PA) hydrogels have great potential for biomedical applications, owing to their high toughness and good self-recovery and self-healing (SELF) behavior in addition to their physical properties similar to human tissue. However, their implementation as practical biomedical skin patches or wearable devices has so far been limited by their insufficient transdermal adhesion strength. In this work, a new polyampholytic terpolymer (PAT) hydrogel with enhanced skin adhesion was developed using a novel and simple strategy that tunes the structure of ion-pair associations (IPAs), acting as cross-links, in the hydrogel via adding an extra neutral monomer component into the network without changing the total charge balance. The PAT hydrogels were synthesized by the terpolymerization of the neutral monomer N,N-dimethylacrylamide (DMAAm) (or 2-hydroxyethyl methacrylate (HEMA)) as well as the cationic monomer 3-(methacryloylamino) propyl-trimethylammonium chloride (MPTC) and the anionic monomer sodium p-styrenesulfonate (NaSS). Their IPA, which determines their network structure, was modulated by varying the feed concentration of the neutral monomer, Cnm. An increase of Cnm within an optimized Cnm window (0.3-0.4 M) decreased the cross-linking density (strength and density of the IPAs) of the PAT hydrogels, reducing the softening temperature and Young's modulus, which increased compliance but maintained sufficient mechanical strength and thereby maximized the contact surface and enhanced skin adhesion. The DMAAm monomers, compared to the HEMA monomers, produced the higher skin adhesion of the PAT hydrogel, which was explained by the difference in their reactivity to the MPTC and NaSS. This study demonstrated this new method to develop the PAT hydrogels with excellent skin adhesion and biocompatibility while maintaining good toughness, compliance, and SELF behavior and the potential of the PAT hydrogels for biomedical skin patches and wearable devices.

Vertebral landmark labelling on X-ray images is important for objective and quantitative diagnosis. Most studies related to the reliability of labelling focus on the Cobb angle, and it is difficult to find studies describing landmark point locations. Since points are the most fundamental geometric feature that can generate lines and angles, the assessment of landmark point locations is essential. The aim of this study is to provide a reliability analysis of landmark points and vertebral endplate lines with a large number of lumbar spine X-ray images. A total of 1000 pairs of anteroposterior and lateral view lumbar spine images were prepared, and 12 manual medicine experts participated in the labelling process as raters. A standard operating procedure (SOP) was proposed by consensus of the raters based on manual medicine and provided guidelines for reducing sources of error in landmark labelling. High intraclass correlation coefficients ranging from 0.934 to 0.991 verified the reliability of the labelling process using the proposed SOP. We also presented means and standard deviations of measurement errors, which could be a valuable reference for evaluating both automated landmark detection algorithms and manual labelling by experts.

The prevalence of lumbosacral radiculopathy is estimated to be approximately 3% to 5% in patient populations. Lumbosacral radiculopathy is largely caused by a complex interaction between biomechanical and biochemical factors. Nerve block therapy (NBT) mainly treats lumbosacral radiculopathy by improving the biochemical factors, whereas acupotomy mainly focuses on improving the biomechanical factors. Therefore, it is thought that synergistic effects may be obtained for the treatment of lumbosacral radiculopathy when both NBT and acupotomy are combined. However, no study in China and Korea, where acupotomy is majorly provided, has reported the effects of such a combination treatment. Therefore, this study aimed to evaluate the safety, effectiveness, and cost-effectiveness of the concurrent use of a deeply inserted acupotomy and NBT for the treatment of lumbosacral radiculopathy.This is an open-label, parallel, assessor-blinded, randomized controlled trial, which will include 50 patients with lumbosacral radiculopathy. After patients voluntarily agree to participate in the study, they will be screened, and will undergo necessary examinations and tests according to the protocol. Those who satisfy the selection criteria will be randomly assigned to either the NBT + acupotomy or NBT groups in a 1:1 ratio. Both groups will undergo 2 NBTs once every 2 weeks from 1 week after the screening test. The treatment group will receive additional acupotomy twice a week for 4 weeks. The primary endpoint is the Oswestry Disability Index, whereas the secondary endpoints are the Numeral Rating Scale, European Quality of Life 5-dimension, McGill pain Questionnaire, Roland-Morris Disability Questionnaire, safety assessment, and economic feasibility evaluation. The measurements will be made at 0, 2, 4, and 8 weeks.This trial has received complete ethical approval from the Ethics Committee of Catholic Kwandong University International St. Mary's Hospital (IS20OISE0085). We intend to submit the results of the trial to a peer-reviewed journal and/or conferences.

This paper presents a new surface modification strategy to develop a poly(ethylene terephthalate) (PET)-based membrane having a hydrophilic surface, high nutrient ion permeability, sufficient mechanical strength, and organic fouling resistance, using an anthracene (ANT)-attached polyethylene glycol (PEG) surface modification agent (SMA) synthesized in this work. During the modification process, the ANT parts of the SMAs poke through and anchor to the surface of a commercial PET woven fabric via physical interactions and mechanical locking. The PEG chain parts coat the surface in the brush and arch forms, which generates a hydration layer on the fabric surface. The consequently obtained surface property and unique structure of the modified PET-based membrane result in higher nitrate ion permeability, organic fouling resistance, and microalgae production compared to those of the unmodified one. These are also affected by the molecular weight of the PEG and the number density of the anchored SMAs. The study demonstrates that this new surface modification method has the potential to allow the development of a desirable PET-based membrane for the efficient massive production of marine microalgae.

Three-dimensional (3D) porous materials gain considerable attention in electronics and biomedical/environmental engineering owing to their high porosity, large surface area, and controllable morphological and mechanical properties. In this work, reversibly compressible feather-like lightweight 3D chitosan/graphene oxide (CS/GO) composite foams were prepared with varying the composition ratios of CS to GO using a freeze-drying method. Their structure was obtained via amide linkage formation between the CS amine groups and GO carboxylic acid groups throughout the foam. Chemical analysis of the foams was performed using Fourier-transform infrared spectroscopy, and their morphology was analyzed by field-emission scanning electron microscopy and crosslinking density measurements. Their mechanical features and static and dynamic viscoelastic properties were characterized by monotonic compression, stress-relaxation, and frequency sweep tests using a custom-built micro-indenter and dynamic mechanical analyzer. With increasing the CS concentration, their storage/loss modulus and crosslinking density increased, while their tanδ decreased. Their viscoelastic properties predicted using the proposed modified micromechanics models agreed with the experimental data. This study demonstrates a simple strategy to produce lightweight porous 3D CS/GO composite foams with biocompatibility, electrical conductivity, and decent mechanical and viscoelastic properties regulated by the composition. These foams are promising materials applicable in biomedical and environmental engineering and electrical devices.

Graphene oxide (GO) attracts tremendous attention for application in high-performance stimuli-responsive “smart” materials because of its unique and excellent electrical, mechanical, thermal, and optical properties, high biocompatibility, and potential application in a variety of fields, including nanocomposite-based devices. Even at an extremely small loading, the chemical, physical, and mechanical properties of GO-polymer nanocomposites can be significantly changed due to its one-atom thickness and large surface area. Therefore, GO-based filler-containing polymer nanocomposites are sensitive to various external stimuli, such as electric and magnetic fields, pH, thermal or optical excitations, and stress. This article reviews the compositions, preparations, and characteristics of a variety of external stimuli-responsive nanocomposites containing GO and other graphene-based fillers. Particularly, the electrorheological and magnetorheological behaviors of smart fluids are described with well-known models and relationships. Finally, various applications of GO-polymer nanocomposites are briefly presented.

Before Chuna manual therapy (CMT), a manual therapy applied in Korean medicine, CMT spinal diagnosis using palpation or X-ray is performed. However, studies on the inter-rater concordance of CMT diagnostic methods, concordance among diagnostic methods, and standard CMT diagnostic methods are scarce. Moreover, no clinical studies have used artificial intelligence (AI) programs for X-ray image-based CMT diagnosis. Therefore, this study sought a feasible and standard CMT spinal diagnostic method and explored the clinical applicability of the CMT-AI program. One hundred participants were recruited, and the concordance within and among different diagnostic modalities was analyzed by dividing them into manual diagnosis (MD), X-ray image-based diagnosis (XRD) by experts and non-experts, and XRD using a CMT-AI program by non-experts. Regarding intra-group concordance, XRD by experts showed the highest concordance (used as a gold standard when comparing inter-group concordance), followed by XRD using the AI program, XRD by non-experts, and then MD. Comparing diagnostic results between the groups, concordance with the gold standard was the highest for XRD using the AI program, followed by XRD by non-experts, and MD. Therefore, XRD is a more reasonable CMT diagnostic method than MD. Furthermore, the clinical applicability of the CMT-AI program is high.

Supplemental Digital Content is available in the text, Background: Chemotherapy-induced peripheral neuropathy (CIPN) occurs in 68.1% of patients within the first month of undergoing chemotherapy; however, standardized treatment for CIPN has not been established yet. The efficacy of acupuncture, a widely used treatment for CIPN in South Korea, has not been studied sufficiently. This study aimed to review the studies that evaluated the efficacy of acupuncture or electroacupuncture (EA) in treating CIPN. Methods: A literature search was performed on relevant international databases — MEDLINE, Embase, the Allied and Complementary Medicine Databases, and China National Knowledge Infrastructure — as well as Korean databases — the National Digital Science Library, Oriental Medicine Advanced Searching Integrated System, DBpia, and Korean Studies Information Service System. Randomized controlled trials (RCTs) that aimed to treat CIPN symptoms with acupuncture or EA and set not only a control group with a conventional pharmacological treatment or injection, but also a placebo control or sham-acupuncture group, were included. Meta-analysis was conducted to elucidate the efficacy of acupuncture/EA on the basis of symptom score. Results: Of the 13 studies included in the literature review, 12 RCTs compared acupuncture and pharmacological treatments. There were 3 EA RCTs, but only 1 RCT compared EA and sham-EA. A total of 832 participants were included in these studies. Five RCTs showed that acupuncture was more effective than pharmacological treatment in terms of efficacy rate. Regarding the risk of bias summary, the quality of included studies was poor. Only 1 study compared the efficacy of EA and sham EA; therefore, the specific efficacy of acupuncture could not be elucidated. Conclusion: Acupuncture is safe, but the symptom-alleviating effect on CIPN can hardly be determined because of methodological deficiencies of the included studies. In terms of the clinical efficacy rate, acupuncture was more effective than conventional pharmacological treatments. PROSPERO registration number: CRD42018111509.

The purpose of this study was to investigate and compare the clinical and radiological results of ORIF with inter-fragment screw or buttress plate fixation of acute PIP joint fracture dorsal dislocation. Between January 2007 to December 2016, nineteen patients - 14 men and 5 women with an average age of 40.9 (19 to 64) years - were included in this study; 9 patients underwent small sized interfragmentary screw fixation and 10 patients underwent small buttress plating. The average follow-up period was 45.1 (13 to 78) months. Clinical assessment included measurement of range of motion (ROM) of the proximal and distal interphalangeal joint (PIP, DIP), grip and pinch strength, and pain with use of the Visual Analog Scale (VAS). At the postoperative X-ray, articular step off, gap, and degree of dorsal subluxation was measured, and maintenance of the reduction, fracture union, and the presence of degenerative changes were assessed. All patients achieved solid unions without instability. The overall average range of motion of PIP joint were from 9° to 85° (10-83° in the screw group, 8-87° in the plate group without significant difference). However, the screw group (average: 53°) presented more flexion in the distal interphalangeal joint than the plate group (average: 34°). Plate fixation can cause limited DIP flexion. Six of the ten patients from the plate group, underwent implant removal and two of these patients required PIP joint arthrolysis due to the PIP flexion contracture of more than 30°. Three of the nine patients in screw group underwent implant removal and two of the three patients required PIP joint arthrolysis. Mini plate and screw fixation of acute PIP joint fracture dorsal dislocation can achieve comparable favorable clinical and radiographic outcomes through stable fixation and early range of motion exercise. Screw fixation, if possible, is probably preferable to plate fixation because of better DIP joint ROM and lower incidence of hardware removal. If there is a need for plate fixation the use of a short plate is recommended to avoid joint stiffness.ZIEL: In dieser Studie wurden die klinischen und radiologischen Ergebnisse nach Schraubenosteosynthesen mit den Ergebnissen von Plattenosteosynthesen von dorsalen Luxationsfrakturen des Fingermittelgelenkes (PIP-Gelenk) verglichen. Zwischen Januar 2007 und Dezember 2016 wurden 19 Patienten – 14 Männer und 5 Frauen mit einem durchschnittlichen Alter von 40,9 (19–64) Jahren in die Studie eingeschlossen. Bei 9 Patienten erfolgte eine Schrauben-, bei 10 Patienten eine Plattenosteosynthese. Die Nachuntersuchungszeit betrug im Schnitt 45,1 (13 bis 78) Monate. Die klinische Untersuchung umfasste die Messung des Bewegungsumfangs des Mittel- und Endgelenkes (PIP- und DIP-Gelenk), der Grobgriff- und Spitzgriffkraft sowie der Schmerzen mittels visuellen Analogskala (VAS). Die postoperativen Röntgenbildern wurde bzgl. Frakturheilung, Repositionsverlust, degenerativen Veränderungen und der Größe verbliebener Stufen- und Spaltbildungen ausgewertet. Bei allen Patienten kam es zur knöchernen Heilung ohne Zeichen einer Instabilität des PIP-Gelenkes. Die durchschnittliche Beweglichkeit aller PIP-Gelenke betrug 0–9–85°, für die Schraubengruppe 0–10–83°und für die Plattengruppe 0–8–87°, ohne dass ein signifikanter Unterschied bestand. Im DIP-Gelenk wiesen Patienten der Schraubengruppe eine bessere Flexion auf. Bei 6 der 10 Patienten mit Plattenosteosynthese musste die Platte entfernt werden, gleichzeitig erfolgte bei 2 eine Lösung des PIP-Gelenkes aufgrund einer Beugekontraktur von mehr als 30°. Bei 3 der 9 Patienten mit Schraubenosteosynthese erfolgte ebenfalls die Entfernung des Osteosynthesematerials, 2 erhielten zusätzlich eine Lösung des PIP-Gelenkes. Schrauben- und Plattenosteosynthesen dorsaler Mittelgelenksluxationsfrakturen erzielen vergleichbar gute klinische und radiologische Ergebnisse und erlauben eine Frühmobilisation bei stabiler Situation. Aufgrund der besseren Beweglichkeit im DIP-Gelenk und da weniger häufig das Osteosynthesematerial entfernt werden muss, ist – wenn möglich – die Schraubenosteosynthese zu bevorzugen. Bedarf es einer Plattenosteosynthese, sollte die Platte möglichst kurz sein, um Bewegungseinschränkungen des DIP-Gelenkes zu vermeiden.

Polycarboxylates in chemical admixtures are adsorbed onto the surface of cement particle, and the degree of their adsorption is related to the performance of concrete. Measuring total organic carbon (TOC), we demonstrated the amount of the consumed carbon is consistent regardless of the existence of aggregates. This result allows us to consider the effect of aggregates inclusion in a superplasticized cement paste. In a multiscale approach, concrete or mortar is considered as suspension of aggregates in cement paste. Excess paste layer covering aggregates in cement-based materials is considered taking a material property of the layer thickness in addition to the volume fraction of the aggregates. Finally, the yield stress of mortar or concrete can be predicted assuming that the layer thickness is constant regardless of the aggregate volume fraction.

The use of injectable hydrogel formulations have been suggested as a promising strategy for the treatment of degenerative disc disease to both restore the biomechanical function and reduce low back pain. In this work, a new thermo-sensitive injectable hydrogels with tunable thermo-sensitivity and enhanced stability were developed with N-hexanoylation of glycol chitosan (GC) for treatment of degenerative disc disease, and their physico-chemical and biological properties were evaluated. The sol-gel transition temperature of the hydrogels was controlled in a range of 23–56 °С, depending on the degree of hexanoylation and the polymer concentration. In vitro and in vivo tests showed no cytotoxicity and no adverse effects in a rat model. The hydrogel filling of the defective IVD site in an ex vivo porcine model maintained its stability for longer than 28 days. These results suggest that the hydrogel can be used as an alternative material for treatment of disc herniation.

The aim of this research was to investigate the validity of the Krieger–Dougherty model as a quantitative model to predict the viscosity of mortar depending on various aggregate sizes. The Krieger–Dougherty model reportedly predicted the viscosity of a suspension, which includes cement-based materials. Concrete or mortar incorporates natural resources, such as sand and gravel, referred to as aggregates, which can make up as much as 80% of the mixture by volume. Cement paste is a suspending medium at fresh state and then becomes a binder to link the aggregate after its hydration. Both the viscosity of the suspending medium and the characteristics of the aggregates, therefore, control the viscosity of the cement-based materials. In this research, various sizes and gradations of fine aggregate samples were prepared. Workability and rheological properties were measured using fresh-state mortar samples and incorporating the various-sized fine aggregates. Yield stress and viscosity measurements were obtained by using a rheometer. Based on the packing density of each fine aggregate sample, the viscosity of the mortar was predicted with the Krieger–Dougherty model. In addition, further adjustments were made to determine the water absorption of fine aggregates and was transferred from successful experiment to simulation for more accurate prediction. It was also determined that both yield stress and viscosity increase when the fine aggregate mean size decreases throughout the mix. However, when the mean size of the fine aggregates is bigger than 0.7 mm, the yield stress is not affected by the size of the fine aggregate. Additionally, if aggregate grains get smaller up to 0.3 mm, their water absorption is critical to the rheological behavior.

Magnetic and semiconducting Fe3O4/poly(o-anisidine) (POA) core/shell composite particles were fabricated by an oxidation process using Fe3O4 synthesized separately. The dispersion stability in a liquid medium and the electrical conductivity of synthesized particles were improved because of the conductive POA polymeric shell. The morphological, microstructural, compositional/elemental, and thermal behaviors of the particles were characterized using SEM with energy dispersive X-ray spectroscopy, TEM, XRD, and thermogravimetric analysis, respectively. A smart electro-magneto-rheological suspension containing Fe3O4/POA particles with two functionalities, magnetism and conductivity, was prepared. Its electrorheological properties were investigated at different electric field strengths using a rotational rheometer. Without an electric field, the sample demonstrated typical Newtonian fluid behavior, as expected. However, while under the electric field, it exhibited a solid-like behavior, and the dynamic (or elastic) yield stress of the ER fluid increased linearly as a function of the electric field strength in a power-law function with an index of 2.0, following the polarization mechanism.

Advance in high-range water-reducing admixture revolutionizes the workability and constructability of conventional vibrated concrete as well as self-consolidating concrete. Its need from construction fields has increased, and consequently a variety of new-type polycarboxylates, base polymers for the admixture, are being formulated in these days. Synthesizing new polymers needs a quick, but reliable, test to evaluate its performance on concrete. The test is also asked for selecting the best applicable brand of them before a test concrete will be mixed. This paper proposes a “channel flow test” and its usage for the purpose. The proposed procedure for the test includes the mix proportion of a test mortar, the test method, and rheological interpretation of the test results.

The acid-base junction potential can be used to generate electricity instead of the reduction-oxidation potential, which is often used for energy conversion between chemical energy and electricity. In this study, reverse bipolar electrodialysis was designed for energy conversion between acid-base solutions and electricity. Operating a flow battery with various HCl/NaOH concentrations, or an ABJFB, the current-voltage relationships showed typical polarization curves that were similar to those obtained in power generation from a fuel cell. We further demonstrated that the cell can be operated in a charge/discharge cyclic mode in a single cell. To the best of our knowledge, this study is the first report on a proof-of-concept experiment demonstrating the cyclic operation of an ABJFB. Keywords: Bipolar membrane, Water splitting, Reverse electrodialysis, Energy storage system, Acid-base generation, Ion exchange membrane

Conventional and herbal drugs are frequently used together to treat many disorders. Samryungbaekchul-san (SRS, a herbal formula) and otilonium bromide (OB, an antispasmodic agent) are widely used to treat diarrhea-predominant irritable bowel syndrome (D-IBS) in Eastern Asian countries. However, there have been no studies on the co-administration of SRS and OB. Therefore, we aimed to preliminarily assess the feasibility of SRS combined with OB for D-IBS treatment in a pilot double-blind, four-arm, parallel-group, randomized controlled trial (RCT), including 80 patients diagnosed with D-IBS according to the Rome III criteria. The patients were randomly assigned to four treatment groups and were administered drugs for eight weeks after a two-week preparatory period. Follow-up was conducted four weeks after the administration period. The primary outcome was evaluated by using a global D-IBS symptom improvement score, no statistically significant difference was observed between the groups. However, multiple logistic regression analysis of primary outcome scores shows that SRS significantly improved D-IBS symptoms (p &lt, 0.05). For secondary outcomes, better results were observed in the SRS + OB group, in terms of symptoms, including abdominal pain, discomfort, frequency of abdominal pain, and stool form than in OB alone or placebo groups (p &lt, 0.05). In conclusion, the co-administration of SRS and OB might be an effective and safe strategy for the treatment of D-IBS. Large-scale RCTs are warranted to further confirm and clarify these findings.

Introduction Total knee replacement (TKR) is a surgical procedure that is being increasingly performed as a result of population aging and the increased average human life expectancy in South Korea. Consistent with the growing number of TKR procedures, the number of patients seeking acupuncture for relief from adverse effects, effective pain management, and the enhancement of rehabilitative therapy effects and bodily function after TKR has also been increasing. Thus, an objective examination of the evidence regarding the safety and efficacy of acupuncture treatments is essential. The aim of this study is to verify the hypothesis that the concurrent use of acupuncture treatment and usual care after TKR is more effective, safe, and cost-effective for the relief of TKR symptoms than usual care therapy alone. Methods/design This is an open-label, parallel, assessor-blinded randomized controlled trial that includes 50 patients with TKR. After screening the patients and receiving informed consent, the patients are divided into two groups (usual care + acupuncture group and usual care group); the patients will then undergo TKR surgery and will be hospitalized for 2 weeks. The patients will receive a total of 8 acupuncture treatments over 2 weeks after surgery and will be followed up at 3, 4, and 12 weeks after the end of the intervention. The primary outcome is assessed using the Korean version of the Western Ontario and McMaster Universities Arthritis Index (K-WOMAC), and the secondary outcome is measured using the Numerical Rating Scale (NRS), Risk of Fall, and Range of Motion (ROM). Moreover, the cost per quality-adjusted life years (QALYs) is adopted as a primary economic outcome for economic evaluation, and the cost per NRS is adopted as a secondary economic outcome. Ethics and dissemination This trial has received complete ethical approval from the Ethics Committee of Catholic Kwandong University International St. Mary's Hospital (IS17ENSS0063). We intend to submit the results to a peer-reviewed journal and/or conferences. Trial registration ClinicalTrials.gov Identifier: NCT03633097.

모르타르를 포함한 건설재료의 작업성은 시공 품질을 결정짓는 중요한 요소 중 하나이다. 콘크리트 등 건설재료의 작업성을 정량적으로 표현할 수 있는 레올로지 특성은 상용화된 레오미터를 통해 측정할 수 있지만, 경제적 또는 공간적 제약으로 인해 실제 시공현장에서의 사용에는 한계가 있다. 많은 건설현장에서는 콘크리트 또는 모르타르의 작업성을 평가 하기 위해 슬럼프 플로 시험 등을 통해 정성적으로 재료의 시공성능을 평가하고 있다. 이 논문에서는 시공현장에서 간편하게 모르타르의 레올로지 특성을 측정할 수 있는 채널 플로 시험과 레올로지 특성과의 상관관계식을 제안하고자 한다. 이를 위해 서 VOF기법을 이용한 유동 해석을 진행하였으며, 유동 시뮬레이션 결과를 로그함수 모델로 일반화하여 채널 플로 길이와 정지시간을 데이터베이스화 하였다. 수립된 데이터베이스를 기준으로 최소 자승법을 이용한 회귀분석을 진행하였고, 결과적 으로 6개의 매개변수로 구성된 모르타르의 채널 플로 시험 결과와 레올로지 특성의 상관관계식을 도출하였다. 또한, 상용 레오미터로 측정한 레올로지 특성과 채널 플로 실험결과로부터 예측된 레올로지 특성을 비교검증 함으로써 제안된 상관관계 식의 현장적용 가능성을 확인하였다.

In this study, the thermal performance of cylindrical heat sinks filled with phase change material (PCM) is investigated for high-power transient cooling. Herein, n-eicosane present in heat sink cavities is used as the PCM, whereas aluminum is used as the heat sink material. For the PCM-based cylindrical heat sink, a two-dimensional numerical model is constructed to determine the influence of various geometrical and thermal parameters, such as fin height, cavity angle, fin angle, base thickness, and power level, on the PCM melting process. All parametric simulations were performed using the heat sink unit cell by exploiting the symmetry. Results show that the PCM melting time can be increased by increasing the amount of PCM filling the cavity and increasing the mass of the heat sink material. Furthermore, dimensional analysis generalizes the obtained numerical results. The PCM melt fraction and corresponding Nusselt number are generalized in terms of a combination of the Fourier, Stefan, and Rayleigh numbers by introducing the effective heat flux to account for three-sided wall heating for the cylindrical heat sink. New correlations for predicting the PCM melt fraction and Nusselt number during the PCM melting process in cylindrical heat sinks are proposed as a function of the combination of dimensionless groups.

Relatively monodispersed poly(diphenylamine)/polyaniline (PDPA/PANI) core/shell composite nanospheres were fabricated by an oxidative polymerization, both in the dispersed phase of diphenylamine and at the interface between the suspended and continuous phases. A reactive surfactant synthesized with aniline and sodium dodecyl sulfate was adopted. The fine core/shell structure formation via π-π stacking between the aromatic rings of PDPA and PANI was confirmed by analyzing the chemical composition, morphology, and crystallinity of the particle components. An electrorheological (ER) fluid was fabricated by suspending the PDPA/PANI nanoparticles in silicone oil, and its ER behaviors were characterized by the controlled shear stress and rate, dynamic oscillation, and on-off electrical field tests. The ER fluid under an electric field exhibited an immediate phase transition, viscoelasticity, and three measurement-dependent yield stresses. In addition, its stable shear stresses over a wide range of shear rates were fitted smoothly by the CCJ model and were shown to increase with increasing EF strength. Moreover, the dielectric characteristics and Cole-Cole analysis of the ER fluid confirmed the effective ER property. The PDPA/PANI-based ER fluid possessing an instantaneous and controllable electro-response is believed to be a promising system for intelligent control applications.

Novel semi-conductively encapsulated microspheres were fabricated by coating poly(diphenylamine) (PDPA) onto spherical silica particles via chemical oxidative polymerization. Their nanoscale-encapsulated spherical structure and PDPA shell thickness of approximately 30 nm were observed by both SEM and TEM. Fourier transform infrared spectroscopy confirmed the successful surface-modification of silica particles with PDPA, which was probably obtained through π−π* stacking interactions between the aromatic groups of PDPA and n-[3-(trimethoxysilyl) propyl]aniline as a grafting agent attached to the silica surface. Thermogravimetric analysis revealed the reasonable thermal stability of the fabricated particles. The electrorheological (ER) suspension (10 vol%) with the silica/PDPA composite microspheres was fabricated without a typically used de-doping process. Their dynamic and elastic yield stresses increased with applied electric field strength, following the power-law model (~E1.5). Their shear stress and their solid-like behavior were explained using the Herschel-Bulkley model and Schwarzl equation, respectively. The immediate and reversible response of the ER fluids was observed using on-off tests.