bluuebunny/crossref_metadata_2025 huggingface dataset:
THE SOUND ABSORPTION OF AN ISOLATED RESONATOR WITH A CROSS-SHAPED SLIT AND ITS DEPENDENCE ON THE NUMBER OF RESONATORS/VIENETINIO AKUSTINIO REZONATORIAUS SU KRYŽIAUS FORMOS PLYŠIU ABSORBCIJA IR JOS PRIKLAUSOMYBĖ NUO REZONATORIŲ KIEKIO
Authors: Stauskis Vytautas
Published: March 2019

Teoriškai nagrinėjama vienetinio, didelių matmenų akustinio rezonatoriaus su kryžiaus formos plyšiu garso absorbcijos, plyšio impedanso realių ir menamų dalių priklausomybė nuo rezonatorių kiekio. Skaičiavimais nustatyta, kad garso absorbcija priklauso nuo rezonatorių kiekio. Vienas rezonatorius, kurio plotas 4,3 m2, o plyšio plotis 50 cm esant 125 Hz absorbuoja apie 5 m2 garso energijos. Kai rezonatorių skaičius padidėja iki 2, absorbcija siekia 27 m2. Didėjant rezonatorių skaičiui iki 4,6 ir 8, garso absorbcijos plotas atitinkamai padidėja iki 180, 400 ir 900 m2. Didėjant rezonatorių skaičiui, platėja dažnių sritis, kurioje garso absorbcija turi dideles reikšmes.

Plyšio impedanso realios dalys, didėjant rezonatorių skaičiui mažeja ir jos auga didėjant dažniui. Tai ypač ryšku esant žemiems dažniams. Plyšio impedanso menamos dalys, didėjant rezonatorių skaičiui, mažai priklauso nuo dažnio ir esant žemiems dažniams jos mažėja, didėjant rezonatorių skaičiui.

Eksperimentiniai tokio rezonatoriaus tyrimai rodo, kad maksimali jo absorbeija esant 100 Hz siekia 4–6 m2, ir tai priklauso nuo matavimo taško. Toks rezonatorius, kurio tūris yra lik 7,8 m3 turi didelį reverberacijos laiką. Matuojant pagal lygį 0—30 dB, jo maksimalios reikšmės dažnių diapazone 400—800 Hz siekia 0,8—1,2 s. Ankstyvas reverberacijos laikas siekia 1—1,4 sekundes ir turi ryškų maksimumą esant vidutiniams dažniams. Šis rodiklis taip pat priklauso nuo matavimo taško.

Akustinio svorio centro reikšmės siekia maksimumo esant vidutiniams dažniams. Jo reikšmės śiame diapazone yra žymiai didesnės negu esant žemiems ir aukštiems dažniams. Šis rodiklis gerai koreliuoja su ankstyvuoju reverberacijos laiku.

Garso absorbcijos koeficiento kitimo charakteris yra toks pat. kaip ir garso absorbcijos. Jo maksimalias reikšmes gauname esant 100 Hz, jos siekia 0,17—0,27 ir priklauso taip pat nuo matavimo taško. Tai rodo, kad vienetinis rezonatorius su kryžiaus formos plyšiu gerai absorbuoja garso energiją esant žemiems dažniams ir kad garso laukas rezonatoriuje yra netolygus.

Toks rezonatorius ne tik gerai absorbuoja garso energiją, bet ir didelę jos dalį grąžina atgal į aplinką. Toks akustinis reiškinys gali padėti koreguojant jau pastatytos salės akustiką, tam visai nenaudojant garsş absorbuojančių medžiagų.
NUMERICAL INVESTIGATIONS OF HEAT TRANSFER IN A TROMBE'S WALL/SKAITINIS ŠILUMOS PERDAVIMO TROMBE'S SIENOJE TYRIMAS
Authors: Koczyk Halina , Górka Andrzej
Published: March 2019

Straipsnyje nagrinějama, kaip taikyti baigtinių skirtumų metodą šilumos perdavimo modeliui sukurti pastatams, kurie naudojasi pasyviaja saulės sistema, ypaě tiesiogine ar netiesiogine. Pateiktieji algoritmai bei skaičiavimo programa gali būti taikomi šiluminěs pusiausvyros elementams tirti nurodyto tipo pastatuose, be to, nustatyti ir vėdinimo efektyvumui Trombe's sienoje, pasižyminčioje savitakiu oro srautu vidinėmis tuštumomis.

Straipsnyje pateikiamas Poznanės lauko klimato modelis, pagrįstas vidutiniais metų duomenimis. Pateikti ir Poznanės klimato sąjygoms būdingi pavyzdiniai rezultatai, susiję su šiluminės pusiausvyros elementais patalpoje su pasyviąja saulės sistema. Įvertintas ir oro kaitos greitis Trombe's sienoje su savitakiu oro srautu, susidarančiu dėl tankio skirtumių.
A NEW RETARDING AGENT OF BUILDING GYPSUM HARDENING/NAUJAS STATYBINIO GIPSO KIETĖJIMO LĖTIKLIS
Authors: Kazragis Algimantas , Marčiukaitis Glntaras , Jurkėnas Gediminas
Published: March 2019

In order to inhibit the process of setting and hardening of building gypsum, retarding agents are used. They:

decrease the solubility of gypsum semihydrate (e.g. ammonia)

form compounds of lower solubility on the surface of gypsum grains (sodium and potassium phosphates, tetraborate, boric acid)

are absorbed on gypsum grain surface and inhibit the formation of crystal nuclei (sulphite alcohol ferment, keratin).

The materials mentioned above have some disadvantages:

long duration of preparation (lying, boiling, filtering) and uncertainty of formulae (glue solutions)

layering of gypsum additions mixtures and decrease of mechanical resistance of hardened gypsum (phosphates, borates)

process complications caused by necessity of water heating that leads to uncertain influence of additions when the conditions for maintaining constant temperature of the mixture are absent (hot running water).

New retarding agent, inhibiting the hardening of building gypsum without disadvantages listed above is created. The effect of the retarding agent is caused by the formation of clathrate compounds. The retarding agent consists of carbamide and inorganic stabilising addition, in ratio 40:1. The duration of the complete hardening of building gypsum can be prolonged by the retarding agent up to 90 min.
INVESTIGATION INTO LOW DENSITY POROUS CONCRETE PENETRABILITY BY AIR/MAŽO TANKIO AKYTOJO BETONO ORO LAIDUMO TYRIMAI
Authors: Laukaitis Antanas , Kunskaitė Laima J.
Published: March 2019

Low-density (250–350 kg/m3) porous concrete has good thermal insulation and acoustical properties. However, the determination of these properties requires a lot of time and is rather costly.

Changes in these properties can be determined, if the porous concrete air penetrability, which can be simply found, is known.

This paper deals with porous concrete made using Portland cement binder and a binder mixture (lime + Portland cement), as well as with foam concrete air penetrability coefficient value dependency on its density and water/dry solids ratio V/K.

The raw materials composition is given in Table 1. Fig. 1 represents the air penetrability determination apparatus scheme.

Air penetrability increases with a decrease of density in porous concrete sample. For example, when V/K=0.6 and product density decreases from 490 to 310 kg/m3, the air penetrability coefficient increases from 2.5·10−7to 13.1·10−7 m3/m·S·Pa.

Porous concrete air penetrability increases with an increase in V/K (Fig. 2.). The air penetrability coefficient increases from 6·6·10−7 to 12.8·10−7 m3/m·S·Pa when the product density is 350 kg/m3 and V/K changes from 0.5 to 0.7. Changes in V/K have a greater influence on low density porous concrete air penetrability. That is why, when slowly hydrating Portland cement is used for porous concrete production, foaming formation mixture temperature is not high, it binds and is cured very slowly. For higher density product pore structures such a slow curing process does not have any effects, because small, spherical pores prevail.

When the water content is increased in the formation mixture, a change in product porous structure is observed, because larger deformed coupled pores are formed and therefore the air penetrability increases. An air penetrability dependency on product density and V/K regression equation (3) is given.

Air penetrability coefficients of porous concrete made using a mixed binder (lime + Portland cement) are given in Table 2. It has been established, that a 20% Portland cement equivalent amount of lime in the binder mixture according to equation 1 and when the V/K ratio increased from 0.52 to 0.65, the some density product air penetrability coefficient of equal density products increased by 3 times, while the lime content in the binder increased from 20 to 80% from formation mixture samples with V/K ratio =0.52.

Air penetrability of porous concrete made using a mixed binding material also depends on concrete density and formation mixture V/K ratio (Fig. 3.).

Cellular concrete air penetrability coefficient values are given in Fig. 4. Cellular concrete differs from porous concrete, because its air penetrability coefficient values decrease with an increase in V/K ratio. This is the reason why cellular concrete air penetrability coefficients are lower than those of porous concrete. Cellular concrete air penetrability coefficient dependency on product density and V/K ratio is expressed by equation 4.
BEAUTOKLAVIO PUTBETONIO ŠILUMINIŲ TECHNINIŲ SAVYBIŲ TYRIMAI/INVESTIGATION INTO NON-AUTOCLAVED FOAM CONCRETE HEAT ENGINEERING PROPERTIES
Authors: Gnip Ivan , Keršulis Vladislovas , Laukaitis Antanas
Published: March 2019

The purpose of this investigation was to determine various density foam concrete heat engineering properties. These properties are not included in valid construction standards [1].

Thermal conductivity of samples was determined at 25°C according to [2], specific heat—[3], vapour permeability—[4] and sorption moisture—[5].

Dry foam concrete thermal conductivity (W/m-K) dependency on its density is given in Fig. 1 as well as after mathematical statistical treatment using the regressive equation [1].

Foam concrete thermal conductivity dependency on its humidity statistical analysis results is given in Table 1, here ΔλW s and ΔλW t is the average absolute thermal conductivity increase for 1% materials moisture according to mass and volume, while and δW s δW t is the same increase, but in percentage value. Foam concrete thermal conductivity dependency on moisture is linear.

The specific heat value for 245 and 840 kg/m3 density foam concrete is 980±50 and 850±50 J/kg·K respectively.

The determined foam concrete sorption moisture is given in Fig. 2 and Table 2. The steep moisture increase at high ambient air humidity is defined by adsorption and the beginning of capillary condensation. This state is not noted in literature curve 2 [7] and evidently due to the short experimental interval.

The vapour permeability results for foam concrete are given in Fig. 3 and using the regressive equation (2). Our results are approximately 13% lower than those given for porous concrete [1].

The calculated thermal conductivity was determined using equation (3), assuming that the sorbtion moisture is equal to the relative air humidity (80–85)% (Table 2). Then 250, 500 and 800 kg/m3 density foam concrete λ(ρ0, Wsk) is equal to 0,12, 0,19 and 0,32 W/m·K respectively.

The foam concrete heat capacity coefficients S, calculated according to formula (4) for temperature fluctuation period z=24 h and according to damp foam concrete density and specific heat are given in Table 3.

Experimental for 260, 500 and 800 kg/m3 density non-autoclaved foam concrete heat engineering values are given in Table 4. For comparison, the denominators (under the line) show the corresponding values for porous concrete given in [1], It is purposive to use in practical calculation specific non-autoclaved foam concrete heat engineering values because these differences are substantial.
THE BOLT—WITH—A CRACK SHAKEDOWN ESTIMATION BY THE METHOD OF ADDITIONAL LOAD/VARŽTO SU DVIPUSIU PLYŠIU PRISITAIKOMUMO TYRIMAS PAPILDOMOS APKROVOS METODU
Authors: Leonavičius Mindaugas , Šukšta Marijonas
Published: March 2019

Straipsnyje analizuojamas varžto (smeigės) prisitaikomumas veikiant pastoviai ašinei jėgai ir simetriškai kintančiam lenkimo momentui. Uždavinys sprendžiamas atsižvelgiant į dvipusio, simetriškai išsidėsčiusio plyšio atsiradimą ir vystymąsi. Medžiaga idealiai tampriai plastiška. Sprendimui taikomas papildomos apkrovos metodas. Išnagrinėti vienpusio plastinės deformacijos kaupimosi ir kintamo ženklo plastinio tekėjimo atvejai. Gautos varžto su plintančiu dvipusiu plyšiu prisitaikomumo zornų ribos. Nustatyta varžto atsarga naudojantis prisitaikomumo diagrama įvairių plyšių gylių atvejais.
Exploring dynamic capabilities, intellectual capital and innovation performance relationship: evidence from the garment manufacturing
Authors: Wendra Wendra , Sule Ernie Tisnawati , Joeliaty Joeliaty , Azis Yudi
Published: March 2019

The notions of dynamic capabilities, intellectual capital, and innovation performance have been examined in many competitive advantage scholarly papers. However, there have been small numbers of management studies that consider the link of dynamic capabilities and intellectual capital in respect of innovation performance. Previous studies tend to argue that dynamic capabilities played a mediator or moderator role on intellectual capital and innovation performance linkage. Therefore, this study seeks to propose a new perspective that dynamic capabilities are the antecedents of intellectual capital leading to innovation performance. Thus, the rationale for this study is to propose a conceptual model and to provide empirical support on the mediator role of intellectual capital in dynamic capabilities and innovation performance linkage. By using accidental and snowballs sampling techniques, this study distributed questionnaires to 297 small and medium enterprises of the garment manufacturing in Indonesia. Partial least square offers the main statistics methodology for data analysis. Results show that dynamic capabilities had a significant influence on intellectual capital and innovation performance. Moreover, intellectual capital partially mediated dynamic capabilities’ influence on innovation performance. Therefore, it is expected that organisations should grow, implement and maintain their dynamic capabilities in order to improve their intellectual capital and innovation outcomes. Lastly, some future studies are suggested.
EXPANDING THE PARADIGM: BRINGING DESIGNERLY PERSPECTIVES INTO CREATIVITY SCHOLARSHIP
Authors: Henriksen Danah
Published: March 2019

Designerly ways of knowing have significant untapped potential to inform creativity research. In this article, I draw upon in-depth interviews with expert design scholars to examine this connection. Thematic analysis reveals how design offers potential lenses on creativity that are not often taken up in dominant psychological discourses around creativity. I situate this by framing the need for design-based knowledge within creativity literature. The findings reflect a view of creativity involving perception, intuition, and ability to re-see the world; creativity as an action-orientated phenomenon; and a focus on the ethics of creativity in an increasingly technology-empowered society. In exploring scholarly definitions of and views about creativity, there are insights on how design offers distinctive viewpoints for paradigms around creativity.
CEMENT STABILIZATION TREATMENT OF LEAD AND NAPHTHALENE CONTAMINATED LATERITIC SOILS
Authors: Oluwatuyi Opeyemi E. , Ashaka Edwin C. , Ojuri Oluwapelumi O.
Published: March 2019

This article presents an investigation on the influence of Ordinary Portland Cement (OPC) as a binder in the stabilization treatment of lateritic soil contaminated with lead or naphthalene. To evaluate the performance of the binder, the contaminated soils were tested for mechanical strength and environmental performance before and after the stabiliza­tion treatment. Results showed that the strength as inferred from the unconfined compressive strength (UCS) and cohesion values increased with the addition of the binder. Cement stabilization of the lead contaminated samples also prompted a reduction in the release of lead below the admissible limit during the leaching test. Cement stabilization of the naphthalene contaminated samples, on the other hand, could not contain the release of naphthalene below the regulatory level during the leaching test. The batch equilibrium adsorption test (BEAT) showed that cement stabilization increased the adsorption capacity of the soil for the contaminants.
PREPARATION OF DESULFURIZING ACTIVATED CARBON FROM CORN STALK AND CHARACTERIZATION OF DESULFURIZING STRUCTURE
Authors: Li Fen , Wang He , Zhang Yanping , Wang Qifei
Published: March 2019

This study investigated the optimal conditions for preparing desulfurizing stalk carbon, using corn stalk as a raw material and zinc chloride as an activator. The structure of stalk carbon was characterized using thermogravimetry (TG), fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Brunauer – Emmelt – Teller (BET). Results found no significant difference in stalk carbon desulfurization properties when using stalk skin, core, or a skin-core mixture as raw material. The desulfurization performance of stalk carbon prepared using a skin-core mixture, was the most effective when the material : liquid ratio was 1:2; activation temperature was 350 °C; and activation time was 70 min. The corresponding H2S adsorption time was 74 min. The large specific surface area of 562.28 m2/g and abundant pore-volume of 0.3851 ml/g was found in the desulfurization stalk carbon prepared using these conditions. The increase in micropores and the abundant oxygen-containing functional surface groups were conducive to H2S adsorption. The desulfurization products were found to be mainly elemental S and sulfite.
Particle-in-cell Simulations of Firehose Instability Driven by Bi-Kappa Electrons
Authors: López R. A. , Lazar M. , Shaaban S. M. , Poedts S. , Yoon P. H. , Viñas A. F. , Moya P. S.
Published: March 2019

We report the first results from particle-in-cell simulations of the fast-growing aperiodic electron firehose instability driven by the anisotropic bi-Kappa distributed electrons. Such electrons characterize space plasmas, e.g., solar wind and planetary magnetospheres. Predictions made by the linear theory for full wave-frequency and wave-vector spectra of instabilities are confirmed by the simulations showing that only the aperiodic branch develops at oblique angles with respect to the magnetic field direction. Angles corresponding to the peak magnetic field fluctuating power spectrum increase with the increase in the anisotropy and with the decrease in the inverse power-law index κ. The instability saturation and later nonlinear evolutions are also dominated by the oblique fluctuations, which are enhanced by the suprathermals and trigger a faster relaxation of the anisotropic electrons. Diffusion in velocity space is stimulated by the growing fluctuations, which scatter the electrons, starting with the more energetic suprathermal populations, as appears already before the saturation. After saturation the fluctuating magnetic field power shows decay patterns in the wave-vector space and a shift toward lower angles of propagation.
Tenofovir and Emtricitabine Resistance among Antiretroviral-Naive Patients in the Canadian Observational Cohort Collaboration: Implications for PrEP
Authors:   The Canadian Observational Cohort Collaboration, Younger Jaime , Raboud Janet , Szadkowski Leah , Harrigan Richard , Walmsley Sharon , Bayoumi Ahmed M , Klein Marina B , Cooper Curtis , Burchell Ann N , Loutfy Mona , Hull Mark , Wong Alex , Thomas Rejean , Hogg Robert , Montaner Julio , Tsoukas Chris , Antoniou Tony
Published: March 2019

Background

The real-world effectiveness of pre-exposure prophylaxis (PrEP) may be influenced by circulating HIV strains resistant to either tenofovir or emtricitabine. Yet, few studies have examined rates of resistance to these drugs in clinical settings.

Methods

We conducted a retrospective cohort study of antiretroviral-naive participants in the Canadian Observational Cohort collaboration who initiated antiretroviral therapy between 2006 and 2014. In separate analyses, we determined the prevalence of pretherapy resistance and cumulative incidence of follow-up resistance to tenofovir and emtricitabine. We used multivariable proportional hazards models to examine associations between baseline variables and the development of resistance.

Results

We studied 6,622 antiretroviral-naive participants initiating therapy, of whom 5,428 (82.0%) had a baseline resistance test. Baseline resistance to tenofovir and emtricitabine was observed in 83 (1.5%) and 21 (0.4%) patients, respectively. Among patients without baseline resistance, the cumulative incidence of resistance to tenofovir and emtricitabine 5 years following treatment initiation was 0.0070 (95% CI 0.0046, 0.0095) and 0.033 (95% CI 0.028, 0.038), respectively. Following multivariable analysis, a baseline viral load ≥100,000 copies/ml was associated with emergence of tenofovir (hazard ratio [HR] 2.88; 95% CI 1.35, 6.15) and emtricitabine (HR 2.27; 95% CI 1.64, 3.15) resistance. Initiating an integrase inhibitor-based regimen and CD4+ T-cell count below 200 cells/mm3 were also associated with resistance to each drug.

Conclusions

We observed a low prevalence of baseline resistance and a low incidence of emergence of resistance to tenofovir and emtricitabine among antiretroviral-naive patients in routine clinical care.
Update on Outcome Measure Development in Large-vessel Vasculitis: Report from OMERACT 2018
Authors: Aydin Sibel Z. , Robson Joanna C. , Sreih Antoine G. , Hill Catherine , Alibaz-Oner Fatma , Mackie Sarah , Beard Susan , Gul Ahmet , Hatemi Gülen , Kermani Tanaz A. , Mahr Alfred , Meara Alexa , Milman Nataliya , Shea Beverley , Tómasson Gunnar , Tugwell Peter , Direskeneli Haner , Merkel Peter A.
Published: March 2019

Objective.

The Outcome Measures in Rheumatology (OMERACT) Vasculitis Working Group seeks to develop validated outcome measures for use in trials for large-vessel vasculitis (LVV).

Methods.

An international Delphi exercise conducted among investigators identified items considered important to measure active disease. In parallel, qualitative research with patients was conducted, including interviews and focus groups.

Results.

Next steps prioritized by the group for LVV include (1) defining disease states (remission, flare, and patient-acceptable symptom state) and (2) selection of patient-reported outcome tools.

Conclusion.

The ultimate goal is to develop an OMERACT-endorsed core set of outcome measures for use in clinical trials of LVV.
Persistent Wheeze in Infants: A Guide for General Pediatricians
Authors: Yu Yolanda , Esther Charles R. , Ren Clement L. , Loughlin Ceila
Published: March 2019

Infants with persistent wheeze is a common diagnostic challenge for the general pediatrician because of the broad differential diagnoses. The initial diagnostic approach should include a comprehensive history, physical examination, and chest radiography. Additional testing may be warranted. Involvement of a pediatric pulmonary subspecialist may also be indicated.

[
Pediatr Ann.
2019;48(3):e110–e114.]
Relationshipping nations: Philippines/US fan art and fan fiction
Authors: De Kosnik Abigail
Published: March 2019

Three fan productions are analyzed that delve into the question of what the Philippines and the United States have meant to one another, what the nature of their multifaceted involvement has been for more than a century, what Filipinos feel about the United States of America, and what Americans feel about the Philippines. Fan art and fan fiction are often laden with affect because it is the fact that fan creators are so affected by their favorite media texts that leads them to create fan works in the first place, and that makes their fellow fans, who understand the affects that inspire them, appreciate their works so deeply. Fan productions about the Philippines/United States are similarly suffused with feelings—the feelings that two nations and two peoples have for one another, which are difficult to define, articulate, and express for Filipinos, Americans, and Filipino Americans.
Race, storying, and restorying: What can we learn from black fans?
Authors: Thomas Ebony Elizabeth , Stornaiuolo Amy
Published: March 2019

Tracing storytelling traditions from historic roots within Black cultures to contemporary fandom, this essay argues for more research and critique on the ways that today's Black fans engage in restorying, with implications for reader response theory, research in digital literacies, and Black studies.
"Bodyminds reimagined: (Dis)ability, race, and gender in Black women's speculative fiction," by Sami Schalk
Authors: Lothian Alexis
Published: March 2019

Review of Sami Schalk. Bodyminds reimagined: (Dis)ability, race, and gender in Black women’s speculative fiction. Durham, NC: Duke University Press, 2018. Paperback, $23.95 (192p) ISBN 9780822370888.
Study on Stress Corrosion Cracking Sensitivity of CrNiMoV Steam Turbine Rotor Steels
Authors: Lin Shu Xian , Huang Yu Hui , Xuan Fu Zhen , Tu Shan Tung
Published: March 2019

The stress corrosion sensitivities of 25Cr2Ni2MoV, 26NiCrMoV10-10 and 30Cr2Ni4MoV low-pressure rotor steels in simulated nuclear steam turbine operation condition were investigated by slow strain rate test (SSRT), and the stress corrosion cracking (SCC) mechanisms were studied by optical microscope (OM), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). Results revealed that the SCC sensitivity of 25Cr2Ni2MoV steel was highest in 3.5wt.%NaCl solution at 180°C, while the SCC sensitivity of 26NiCrMoV10-10 steel and 30Cr2Ni4MoV steel are similar. The SCC sensitivity of CrNiMoV steam turbine rotor steels could be decreased by the increase of Ni element and the decline of mechanical intensity. Cracks initiate from metal surface and then propagate to the inner metal, which showed a form of transgranular cracking.
Experimental Study on Peeling Properties of T Type Brazing Joint
Authors: Duan Peng Yang , Wang Dong Xing , Zhou Guo Yan , Tu Shan Tung
Published: March 2019

As the key component of the high temperature gas cooled reactor (HTGR), the performance of the plate fin heat exchanger determines the working efficiency and life of the HTGR. Although the plate-fin structure has lots of advantages such as high efficiency, compact structure, low manufacturing cost, its application will be affected by the vacuum brazing technology and harsh conditions, like high temperature and high pressure. In the practical application of plate-fin heat exchanger, the process of "splitting" between the fin and the diaphragm is very similar to that of the adhesive joint and the delamination of the composite. In the present study, a T-type specimen was designed for the the peel testing of brazed joints. Five kinds of specimens were designed based on the difference between the weld gap and the thickness of the sample base material. The tests were carried out under 450°C and 650°C at five kinds of loading rates, respectively. The peel force-displacement curves of standard samples were obtained . The maximum peel strength and average peel strength were calculated. In addition, the influence of base metal thickness, brazing gap, loading rate and test temperature on the maximum peel strength were analyzed by controlling variable method. Keywords: brazing joint; T-type peel test
Low Cycle Fatigue Behavior of CP-Ti at Different Temperatures
Authors: Ma Tian Hao , Chang Le , Zhou Chang Yu
Published: March 2019

Low cycle fatigue (LCF) tests are performed on CP-Tiat different temperatures (293K,423K and 523K). It is found that the fatigue life of CP-Tidecreases with temperature. A short cycle hardening phenomenon occurs at the beginning of cyclic deformationat 293K and 423K, followed by cyclic softening untilfailure. At 523K, cycle hardening isexhibited throughout the entire cycle until thefracture. The fatigue-life curves obtained from the tests are constructed using Coffin-Manson-Basquin model. According to the relationship between the four parameters of Coffin-Manson-Basquin model and temperature, the temperature-based life prediction model is further proposed. Scanning electron microscopy observation of fatigue fractures showsthat the fatigue cracks of CP-Tiat 423K and 523K under different strain amplitudes initiate on the surface of fatigue specimens and extend to the fracture zone by the transgranular mode.
Influence Factors of Fracture Mechanics Analysis of Reactor Pressure Vessel under Pressurized Thermal Shock
Authors: Luo Juan , Luo Jia Cheng
Published: March 2019

When the reactor pressure vessel (RPV) is subjected to pressurized thermal shock (PTS), the cooling water injected by the emergency core cooling system (ECCS) will generate a large temperature difference in the wall thickness of the pressure vessel. On the other hand, the fracture toughness of the RPV material decreases a lot under long-term neutron irradiation. Under this condition, the PTS transient may cause a rapid growth of defects in the inner surface of the vessel, resulting in failure of the pressure vessel. In this paper, the fracture mechanics analysis method of RPV under pressurized thermal shock is studied. The thermal analysis and structural analysis of the pressure vessel are performed by finite element method. The stress intensity factor and fracture toughness are obtained through calculation. At the same time, the influence factors of fracture mechanics analysis of RPV under PTS condition are analyzed. The effects of different crack size, crack type, load transient, and neutron irradiation flux on the PTS fracture mechanics analysis results are evaluated. Results show that the larger the ratio of length to depth for axial inner surface cracks, the easier RPV crack grows. Under small break condition, the circumferential cracks are safer than axial cracks. The longer the operating time, the more severe the embrittlement of RPV materials, which will lead to the failure of RPV more easily. For the two typical PTS transients studied in this paper, the re-pressurization condition is safer than the small break condition. The results can provide basis for structural integrity assessment of RPV under PTS condition.
Failure Analysis of Hot Clamp Induced Cracking on Hydrogen Reformer Outlet Pigtail Tubes
Authors: Cao Luo Wei , Xie Guo Shan , Zhao Min Zhen
Published: March 2019

Failure analysis of the hot clamped outlet pigtail tubes connected with hydrogen reformer tube in refineries has been carried out. In this paper, hot clamp induced cracking on Incoloy 800HT outlet pigtail tube of a reformer unit is studied by microscopic observation and mechanical properties testing. Metallurgical evaluation and chemical composition analysis have been performed on both hot clamped cracking tube and no cracking one. Results indicated that the most important parameter affecting the high temperature brittleness of pigtails are the Ni/Cr value, surface grain size and impurity atoms grain boundary segregation.
Estimation of Residual Stress and Plastic Properties of a Material without Plastic Plateau by Using Continuous Spherical Indentation
Authors: Wang Zhan Yu , Zhao Jian Ping
Published: March 2019

This paper presents a method to allow the measurement of residual stress (), yield strength () and strain hardening exponent () of metal materials through continuous spherical indentation test. Based on the analysis of finite element simulation results, a new fitting equation between the indentation response parameter and the material properties was given. The influence of friction on finite element model simulation was also discussed when the residual stress is included in the material. Only three load values are required at each different indentation depths, and the three unknown parameters (, and ) can be obtained through corresponding dimensionless functions. Finally, the validation of the method presented in this paper was verified by simulating the material (SUS304) with the known material parameters in the literature.
The Method to Obtain JR- Curve by Continuous Ball Indentation Method
Authors: Zhang Jia Ming , Guan Kai Shu , Wang Qiong Qi , Fan Si Ning , Chen Guo Yao
Published: March 2019

JR-curve is one of an important index to characterize the fracture properties of metal materials. It is usually determined by multi-sample unloading method and single-sample unloading compliance method recommended by standard methods; In consideration of the similarity between the continuous ball indentation method and the single-sample unloading compliance method, The JR-curve is obtained by using the empirical correlation between effective elastic modulus ED of the continuous ball indentation and the unloading compliance C for single simple in this article. The calculation conducted by the correlation formula of the extension length of crack with unloading compliance C. However, results indicate that the fracture toughness J0.05 obtained by empirical correlation of load-depth curve of continuous spherical indentation is still quite different from those given by the standard test.
A Multi-Surface Plasticity Method for Lower Bound Shakedown Load
Authors: Jappy Alan , Mackenzie Donald , Chen Hao Feng
Published: March 2019

A new direct method for calculation of lower bound shakedown limits based on Melan’s theorem and a novel, non-smooth multi-surface plasticity model is proposed and implemented in a Finite Element environment. The load history is defined by a finite number of extreme points defining the load-envelope of a periodic load set. The shakedown problem is stated as a plasticity problem in terms of a finite number of independent yield conditions, solved for a residual stress field that satisfies a piecewise, non-smooth yield surface defined by the intersection of multiple yield surfaces. The implemented Finite Element procedure is applied to two shakedown problems and the results compared with lower and upper bound elastic shakedown solutions given by the Linear Matching Method, LMM. The example analyses show that the proposed Elastic-Shakedown Multi Surface Plasticity (EMSP) method defines robust lower bound shakedown limits between the LMM lower and upper bound limits, close to the LMM upper bound.
Novel Method to Improve the Imaging Accuracy of Defect Based on Zero-Signal Filling for the Plate
Authors: Zhai Shuang Miao , Chen Shao Jie , Hu Gang Yi , Chen Chao Feng , Zhou Shao Ping
Published: March 2019

Many effective image-based imaging algorithms are available for detecting and locating the defects for plate-like structures. The discrete ellipse imaging algorithm is widely applied in plate-like structures. However, the scattering-wave extracted by the baseline subtraction may easily be impacted by noise and the reflect wave from boundary, which significantly reduces the signal-to-noise (STN) of the scattering wave, and then leads to the degrading of imaging accuracy. To enhance the STN and improve imaging accuracy, a novel method of zero-signal filling is used in the discrete ellipse imaging in this paper. To verify its effectiveness, the imaging experiment with a circular sparse array has been conducted. The experimental results show that the method can effectively resolve the signal delay and enhance the STN of the scattering wave. The imaging accuracy can be improved obviously by this method and the defect can be located accurately.
Fatigue Life Properties of Stainless Steels in Wide Ranged Biaxial Stress State
Authors: Saito Shunsuke , Ogawa Fumio , Itoh Takamoto
Published: March 2019

Multiaxial fatigue tests consisting of push-pull loading and cyclic inner pressure were carried out using hollow cylinder specimens of type 430 stainless and type 316 stainless steels at room temperature. 7 types of cyclic loading paths were employed by combining axial and hoop stresses: a Pull, an Inner-pressure, a Push-pull, an Equi-biaxial, a Square-shape, a LT-shape and a LC-shape. Fatigue lives vary depending on the loading path when those were evaluated by the maximum Mises’ equivalent stress on inner surface of the specimen. The fatigue lives of both the steels showed a similar tendency although some Pull tests take longer fatigue life when cracks initiated from inside surface of the specimen. This study investigated the crack initiation and propagation behaviors as well as the initiation of oil leakage to prove the behavior and discusses life evaluation for two steels under wide ranged biaxial stress state, too.
The Precipitation Behavior and Mechanical Properties of Long Term Serviced HR3C/T92 Dissimilar Joint
Authors: Guan Yue , Cao Tie Shan , Cheng Cong Qian , Zhao Jie
Published: March 2019

The dissimilar weld joint of HR3C steel and T92 steel is widely used in the ultra supercritical (USC) boiler due to the different service conditions of HR3C steel and T92 steel. It is important to study how serviced influenced the HR3C/T92 dissimilar joint. The HR3C/T92 dissimilar joint had already served 51020 h under 605 °C and 26.25 MPa. The microstructure and mechanical properties of the long term serviced HR3C/T92 dissimilar joint were tested by XRD, SEM, EPMA,TEM, the impact testing machine and the creep and stress rupture testing machine. The XRD results show that the weld is mainly γ-Fe, which is similar to the HR3C base metal, while the T92 base metal is mainly α-Fe. The SEM results indicate that serviced HR3C’s precipitation behavior is complicated, cause multiple precipitated phases precipitated during the service. Chain-liked M23C6precipitated along the grain boundary. M23C6phase cause the chromium depletion zone along the grain boundary. T92 base metal precipitated lots of carbide particles during the service. Those carbide particles are around 1 μm. The impact fracture of HR3C base metal is brittle fracture while the impact fracture of T92 base metal is ductile fracture. Moreover, the impact fracture of weld is mixed fracture. Chain-liked M23C6along the grain boundary is the main cause of the brittleness of serviced HR3C steel.The constant strain creep tests were proceeded under 650 °C, 700 °C and 750 °C. The high-temperature creep resistance of HR3C base metal is better than that of T92 base metal after service. The resistant to high-temperature creep of served joint is similar to that of serviced T92 base metal. With the increase of temperature, the creep resistance of the T92 base metal decreases the most. On the contrary, the creep resistance of the HR3C base metal shows the minimum reduction.
Initiation and Propagation Behaviors of Small Fatigue Crack in Titanium Alloy TC4
Authors: Zhu Lei , Hu Xu Teng , Jiang Rong , Song Ying Dong , Qu Shou Dao
Published: March 2019

The initiation and propagation behaviors of small fatigue crack in TC4 were investigated in the present work. Surface replication on the basis of a two-part silicon mixture and confocal laser scanning microscope were used to record and observe the small crack initiation and growth processes at room temperature in air. Results showed that surface cracks initiated from the interfaces between α and β phases. When the crack lengths were below ~200 μm, the crack growth rates exhibited large oscillations and temporary retardations due to the presence of α/β interfaces. The corner crack propagated much faster and might have shielding effect on the surface crack.
Synthesis and Heme Polymerization Inhibitory Activity (HPIA) Assay of Chalcone, Flavone and Flavanone Derivatives
Authors: Suryani Novia , Matsjeh Sabirin , Tri Swasono Respati
Published: March 2019

Chalcone, flavone, and flavanone had been synthesized as candidate of the antimalarial compounds. The chalcone 1was synthesised from 2,4-dihydroxyacetophenone and 4-metoxybenzaldehyde as starting materials using base catalyst KOH via Claisen-Schmidt Condensation. The synthesis flavone 2was carried out by cyclization of chalcone 1using I2 in DMSO, while the flavanone 3was produced by cyclization of chalcone 1using NaOAc as a base catalyst. An in vitro antimalarial activity of the compound 1, 2and 3have been evaluated with the chloroquine diphosphate as a positive control in various concentration, and this assay was carried out according to the Basilico method. The IC50value of compound 1, 2, 3and a positive control were 0.25; 0.62; 1.33 and 0.35 mM, respectively. The result showed that chalcone1with the lowestIC50value is a potential candidate as an antimalarial agent.
Synthesis and Activity Test of Coumarin-Chalcone Derivative as a Colorimetric Sensor for Chicken Spoilage Indicator
Authors: Linggayani Nur Hidayati Dehani Dwi , Purwono Bambang , Mardjan Idham Darussalam
Published: March 2019

Chemosensor of coumarin-chalcone (2) derivative has been synthesized and tested for chicken spoilage indicator. The compound (2) was synthesized from the reaction of 3-acetyl-2H-chromen-one (1) and vanillin with reflux and ultrasonic irradiation methods. The compound (2) exhibited quick and obvious color in sensor label for amines from yellow to dark yellow. Application to detect spoiled chicken showed that color of compound (2) changed at 12 h and 6 d in room and chiller temperature respectively. Thus, compound (2) can be used efficiently for decayed chicken detection.
The Influence of Cu Dopant Concentration on the Optical Properties of Fe3O4/SiO2/TiO2 Nanocomposite
Authors: Putri Utami Aisyiah Restutiningsih , Putra M. Sulthon Nurharman Syah , Musawwa M. Miqdam , Kunarti Eko Sri
Published: March 2019

Fe3O4/SiO2/TiO2dopped Cu with magnetic properties had been succesfully syntesized and characterized. The research was began with the synthesis of magnetite and magnetite covered by silica by co-precipitation and sonication method, and the preparation of Cu-doped TiO2using sol-gel method followed by calcination. The concentrations of Cu were 0%, 1%, 3%, 5%, and 7% (FST0, FST1, FST3, FST5, and FST7). The Fourier Transform Infra Red spectrophotometer (FTIR), X-Ray Diffractometer (XRD), Scanning Electron Microscope-Energy Dispersive X-ray spectrophotometer (SEM-EDX), UV-Specular Reflectance Spectrophotometer (SR-UV), and Transmission Electron Microscope (TEM) were used to characterize the nanocomposite and external magnetic bar was used to separate the nanocomposite in an aqueous media. The Cu concentration affected the band gap energy (Eg) and the optimum result was 2.832 eV in FST7. The best magnetic propertieswas material FST0. The time needed for separate this material with aqueous medium was 372 second.
The Role of Reduced Graphene Oxide Concentration as Ablated Material on Optical Properties of Graphene Quantum Dots
Authors: Murdaka Fiqhri Heda , Kusumaatmaja Ahmad , Isnaeni  , Santoso Iman
Published: March 2019

We report the synthesize of Graphene Quantum Dots (GQDs) using ablation method with reduced Graphene Oxide (rGO) solution as a starting material. We have varied the concentration of rGO as following: 0.5, 2, 5 mg/ml and then have ablated them using 800 nm Ti-Sapphire femtosecond laser to obtain GQDs. From the UV-Vis data, we observed that the more concentration of rGO is being ablated, the more secondary absorption peak at 255.1 nm appeared. This secondary absorption peak is a characteristic of n-π* bonding due to the presence of oxygen defect which occurs as a result of the interaction between the laser and the water in rGO solution. We conclude that the population of oxigen defect in GQDs is increasing, following the increase of rGO concentration and could alter the optical properties of GQD. On the other hand, using Tauc’s plot, we confirm that the increase of rGO concentration as the ablated material does not alter GQDs optical band gap. However, it will slightly reduce both, direct and indirect Oxygen defect related optical band gap.
Thermal and Microstructural Study on Mullite-Based Ceramics from Rice Husk-Alumina Mixtures
Authors: Wahab Rabiatul Adawiyah Abdul , Matori Khamirul Amin , Mazlan Mazlini , Mohammad Maryam
Published: March 2019

This study focuses on the physical and microstructural properties of mullite-based ceramic synthesized by solid-state reaction of rice husk ash (RHA) and alumina (Al2O3). Laser Flash analysis (LFA), Field Emission Scanning Electron Microscopy (FESEM) and Energy-dispersive X-ray spectroscopy (EDX) characterized the effects of the mixtures of RHA and Al2O3 matrix. The results show that the Al2O3rich samples sintered at 1500 °C exhibit the highest thermal diffusivity radiated at 500 °Cwith values varied from 0.258-0.369 mm2/s. The addition of Al2O3 (30-60 wt.%) into RHA enhance the crystallization of mullite on the surface of vitreous particles. The presence of diphasic mullite densified the green bodies,and its crystallites size keep increases (400.78-650.52 nm) by theincrement of the sintering temperature (1200-1500 °C). These results suggested that addition of Al2O3into RHA enhance the thermal diffusivity as the values closer to the thermal diffusivity of pure mullite and have high potential application as thermal insulation material. The properties of mullite-based ceramics listed above such samples M1, where the composition closes to mullite (3:2) have comparable properties to commercialize mullite ceramics.
An Interplay Role between Ammonium and Halide Anions as Additives in Perovskite CH3NH3PbI3
Authors: Supianto Mulya , Suyanta Suyanta , Kartini Indriana
Published: March 2019

Methylammonium lead trihalide perovskites have emerged as attractive materials for solar cell applications. The major eminence of this materials can be crystallized via various solution methods to produce the solid state of thin films. However, the crystallinity of perovskite depends on the composition of perovskites. Here, we study NH4Cl and NH4Br as precursor additives for improving crystallinity of perovskites. Perovskite was synthesized by mixing precursor solutions of CH3NH3I and Pb(Ac)2with or without additives NH4Cl and NH4Br using the one-step spin-coating method. By characterizing the thin films using XRD, SEM and UV-Vis spectrophotometer, we found anion Cl and Br performed an important role toward crystallinity, morphology, and optical absorption of perovskites, respectively. Meanwhile, ammonium has assisted to facile remove the residual DMSO solvent confirmed by FTIR. These results shed light on using ammonium halides as potentially dual side additives in the synthesis of perovskites.
Polyethyleneimine-Modified Quartz Crystal Microbalance and its Characteristics for Detecting Acetic Acid
Authors: Purwati Dewi , Julian Trisna , Nur Hidayat Shidiq , Rianjanu Aditya , Kusumaatmaja Ahmad , Triyana Kuwat , Roto Roto
Published: March 2019

Acetic acid is a clear liquid with a strong smell of acids. The danger of inhaling acetic acid vapors may cause irritation of the nose and throat. At high vapor levels, acetic acid may cause respiratory inflammation and can cause eye irritation and eye damage permanently. New detection methods of acetic acid are urgently required especially for practical applications. In this study, the acetic acid vapor sensor was developed by depositing polyethyleneimine (PEI) layer onto the two QCM substrates using well-known self-assembled monolayers (SAM) method. As results, the sensor was less sensitive to humidity. The sensor also showed high sensitivity and limit of detection limit (0.85 mg/L) to acetic acid.
Chitosan-Pectin-Stearic Acid Film for Controlled-Release of Curcumin
Authors: Siswanta Dwi , Hasanah Fithriya , Octaviani Heni , Mudasir Mudasir
Published: March 2019

The release of curcumin from chitosan-pectin-stearic acid films was studied in the variation of the pH of the buffer solutions, the addition of ethanol in the buffer solution, the amount of loaded curcumin, the amount of stearic acids in the films. The chitosan-pectin films were prepared by addition of 1% acetic acid solution of chitosan into 1% aqueous pectin solution, followed by addition of isopropanol solution of stearic acid. The films were characterized using FT-IR spectrophotometer. The study of curcumin release was performed by soaking the film in buffer-ethanol solutions for 6hand measuring the released curcumin by UV-Vis spectrophotometer. The kinetics of releasing curcumin was analyzed using Korsmeyer-Peppas equations. The result showed that the releasing of curcumin was influenced by the amount of loaded curcumin, the amount of stearic acid in the film and buffer pH of the solution. The optimum releasing rate at buffer pH 7 in 40% ethanol solution was obtained when the amount of curcumin loaded and stearic acid were c.a. 55.5 and 136.4 mg/g film, respectively, which the curcumin release achieved 66.04%. Releasing kinetics of the curcumin followed a Korsmeyer-Peppas model with a rate constant (k) of 7.5270 and n of 0.378. The curcumin release mechanism was mainly based on the diffusion mechanism.