214 research outputs found

    Coagulation for treatment of swine slaughterhouse wastewater

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    In this study, wastewater taken from the Nam Phong swine slaughterhouse, Ho Chi Minh City, was used to evaluate the treatment efficiency of common coagulants, including Alum (Aluminum Sulfate - Al2(SO4)3.18H2O), Poly-Aluminum Chloride (PAC), and Ferrous Sulfate (FeSO4.7H2O), using a jar-test system. The experiments were conducted using the one-factor-at-a-time method to examine three variables which are pH, stirring speed, and coagulant dosage. The results showed that both Alum and PAC perform over 90% removal of colour, turbidity, COD, and total phosphorus (TP) from slaughterhouse wastewater at pH 7 with a stirring speed of 75 revolutions per minute (RPM) and average coagulant dosages of 450 mg/L for Alum and 550 mg/L for PAC. Meanwhile, under the appropriate conditions of pH equal to 10 and 75 RPM with a chemical dosage of 350 mg/L, COD and TP removal efficiencies by Ferrous Sulfate exceed 87%, but those of turbidity and colour only reach 25%. This finding could be a promising coagulation method as a pre-treatment for the swine slaughterhouse wastewater

    Application of the Taguchi method to determine optimized parameters for designing brake of hand winch

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    Brakes are used to stop movement or adjust speed to ensure safety for mechanisms or machines. In this paper, the brake applied to hand winch will be studied. This hand winch has been studied by us in previous stages. However, the disadvantage of the winch is that the drum wall attached to the friction surfaces is not reasonable in terms of layout, as well as the parameters to optimize braking moment have not been calculated. A new brake structure is proposed in this study to solve the above problem. This structure does not use the drum wall as the friction surface. It does not affect the drum wall and it is easy to replace the friction surface when necessary. Instead, the cone brake is suitable for the structure brake and the size, structure, and design load. To determine the optimal parameters of the brake structure, the article will analyze the theory, and experiment design. The objective function is the maximum braking torque. Constraints are hand winch parameters, installation, friction surface material, and loading conditions. The corresponding factors are coded according to the Taguchi method, the orthogonal planning matrix is L18. Using Minitab software to analyze the Signal/Noise ratio, the study determined the optimal values for five factors including screw thread pitch, coefficient of friction (screw thread), cone angle, friction coefficient (brake), and large cone brake radius. Research results have selected the optimal parameters of the brake, and the optimal values have satisfied the constraints. The torque at the cone brake is greater than that of the disc brake approximately 37.7 %. The pressure at the friction surface is reduced by about 55 % compared to the disc brake surfac

    Removal of inorganic nutrient and organic carbon from wastewater of Binh Dien market using the green alga Chlorella sp.

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    Traditional markets play a major role in socio-economics and constitutes a significant aspect of Vietnamese culture. However, wastewater streams discharged from the markets are generally characterized by a lot of inorganic nutrients and organic substances originated from fresh food processing units. They could lead to serious water contamination if discharged without proper treatment. This study applied microalgae Chlorella sp. for eliminating inorganic nutrients (NO3--N, NH4+-N and PO43--P) and organic carbon (Chemical oxygen demand-COD) from wastewater of the Binh Dien market. The removal efficiencies reached for NH4+-N > 86%, for NO3--N > 72%, and for PO43--P > 69%, respectively, at algal density of 49 x 104 cell mL-1, and for COD > 96% at algal density of 35 x 104 cell mL-1 after five cultivating days. The effluence satisfied the Vietnamese standard, column B, of the National technical regulation on industrial wastewater (QCVN 40:2011/BTNMT). The results demonstrated that the culture system composed of green algal Chlorella sp. could be a potential candidate for the removal of nutrients and organic carbon by a wastewater treatment process from the Binh Dien market

    Román Frank Herbert Duna v ekokritické perspektivě

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    Cílem této bakalářské práce je analyzovat román Duna (1965) Franka Herberta z hlediska vztahu k ekologii, a dále určit roli toho románu jakožto průkopnického vědeckofantastického díla zaměřeného na ekologii. Teoretická část představuje Dunu v kontextu tvorby Franka Herberta a zároveň i v kontextu děl s podobným zaměřením. Šedesátá léta budou tudíž představena jako přelomová pro vědeckofantastickou literaturu i ekokritiku, tj. nově vzniklý kritický pohled. Praktická část nabízí hlubší ekokritický rozbor Duny s důrazem na roli vody, bleskový technologický vývoj a nahlížení do environmentálních výstrah. Tato práce tedy ve výsledku nabízí ekokritický pohled na Dunu, interpretuje její potenciální ekologická varování a zamýšlí se nad možnými způsoby, jak se vyhnout ekologické katastrofě. Klíčová slova: Frank Herbert, Duna, ekokritika, science-fiction, ochrana vody, těžba zdrojůThis thesis seeks to analyse Frank Herbert's Dune (1965) from the point of view of its treatment of ecology and determine the novel`s role as a pioneering work of science-fiction focussing on ecology. The theoretical part presents Dune within the context of Frank Herbert`s work as well as within the context of other works presenting a similar agenda. Consequently, the 1960s will be presented as the turning point for science-fiction writing as well as ecocriticism, the newly formed critical perspective. The interpretative part offers a deeper ecocritical analysis of Dune, with the emphasis on the role of water, the warp speed technological developments, and perusal of underlying environmental warnings. The thesis thus ultimately presents the ecocritical viewpoint of Dune, interpreting its potential ecological warnings and pondering upon possible ways to avoid ecological disaster. Key words: Frank Herbert, Dune, ecocriticism, science-fiction, water conservation, resource extractionKatedra anglického jazyka a literaturyFaculty of EducationPedagogická fakult

    Remote Working Burnout: Empirical Study from TOE and Technostress Model

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    Work stress and burnout negatively impact the individual and companies. Remote working exacerbates these issues due to the lack of company support and social interactions. Yet, research on identifying factors contributing to stress and burnout in remote workspaces and differentiating the components of stress and burnout in this context is limited. This work presents and empirically evaluates a conceptual framework, based on the Technology – Organization – Environment framework and the technostress theory, which aims to address these gaps. In particular, the model proposed here distinguishes between technostress, work stress, and burnout. Future work to examine the model will use a survey instrument for data gathering, as well as confirmatory factor analysis and partial least squares for analysis

    Purification and characterization of novel fibrinolytic proteases as potential antithrombotic agents from earthworm Perionyx excavatus

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    Six protease fractions, namely FI, FII, FIII-1, FIII-2, FIII-3 and FIV, were isolated from Perionyx excavatus earthworm biomass by acetone precipitation, followed by serial chromatography using anion exchange, hydrophobic interaction and size exclusion chromatography. All fractions exhibited strong hydrolytic activity towards casein. The activity of six fractions towards fibrin, determined by fibrin plate assay, ranged from 44 to 831 plasmin unit.mg-1 and ranked as FIII-3 > FIII-2 > FI > FIII-1 > FIV > FII. Casein degradation was optimal at pH 7 and 11, and at 45-60°C. All fractions were considerably stable at high temperature and wide pH range. They were completely inhibited by phenylmethylsulfonyl fluoride (PMSF). The molecular weights (MW) and isoelectric points (pI) determined by 2D-electrophoresis were 27.5-34.5 kDa, and 4.3-5.2, respectively. Tandem mass spectrometry (MS) analysis was used to deduce the amino acid sequences of some peptides from FIII-1 and FIII-2. The sequences shared 16.9% and 13.2% similarity, respectively, with the fibrinolytic enzymes from two related earthworm species, Lumbricus rubellus and Eisenia fetida. The P. excavatus proteases were classified as serine proteases. They could perform rapid hydrolysis on both coagulated fibrous fibrin and soluble fibrinogen monomers without the presence of activators such as tPA or urokinase

    Lattice-based Public Key Encryption with Multi-Ciphertexts Equality Test in Cloud Computing

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    Nowadays, together with stormy technology advancement, billions of interconnected devices are constantly collecting data around us. In that fashion, privacy protection has become a major concern. The data must be in encrypted form before being stored on the cloud servers. As a result, the cloud servers are unable to perform calculations on en- crypted data, such as searching and matching keywords. In the PKE- MET setting, a cloud server can perform an equality test on a number of ciphertexts which encrypted with the same designated number. In this paper, we propose, for the first time, an efficient construction of a quantum-safe PKE-MET system based on the hardness of the Learning with Errors (LWE) problem in the lattice setting. Furthermore, we also discuss the first lattice-base public key encryption with flexible multi- ciphertext equality test (PKE-FMET) constructions, which allow per- forming equality test on multiple ciphertexts whose designated numbers are less than a threshold number. Our proposed schemes are proven to be secure in the standard model

    Parameter Estimation of LFM Signal in Low Signal-to-Noise Ratio Using Cross-Correlation Function

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    The pulse with intra-pulse modulation plays an important role in the design of radar systems. The first class of the signals type is the linear frequency modulation technique. The linear frequency modulation is used to resolve range resolution problems. This paper provides a new algorithm for detecting linear frequency modulation signals at a low signal-to-noise ratio. The core idea of the proposed method is firstly to analyse the linear frequency modulation signals via Fast Fourier Transform; and then to accumulate all energy to achieve signal detection using cross-correlation methods. The proposed algorithm showed better results in comparison with current algorithms, which are used to estimate the parameters of the linear frequency modulation signals at a low signal-to-noise ratio
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