3,419 research outputs found
Seawater dilution desalination with hybrid FO-RO and UF-RO: Characterisation and assessment of pathogen removal efficacy
No full textThis study investigated the feasibility of embedding two low-energy dilution desalination processes, namely osmotic dilution desalination (ODD; the FO-RO membrane configuration) and mixing dilution desalination (MDD; the UF-RO membrane configuration), in a conventional seawater desalination approach (i.e., seawater reverse osmosis) using real seawater and recycled wastewater. The removal efficacy of bacterial indicators (Clostridium perfringens and Escherichia coli), coliphage genera Microviradae, and Human adenovirus (HAdV) was assessed in influent/effluent samples collected from each membrane configuration. Mixing dilution of the influent feed waters reduced the number of all pathogenic contaminants as well as organic/inorganic compounds. The rejection rate of total suspended solids was 35.7% in FO to 63.6% in UF respectively, whereas that of total organic carbon was 53.8% and 56.9% in FO and UF, respectively. The FO membrane in the ODD process more efficiently removed viruses (5.0 LRV) and bacterial indicators (4.2 LRV) than the UF membrane (3.7 and 3.6 LRV, respectively). Nevertheless, the different methods of detection used in our study, such as culture-based and qPCR, were found to have significant influences on the LRVs. Comparative 16S rRNA sequencing indicated that the vast majority of bacterial indicators in RO permeating from the FO-RO and UF-RO configurations were nonpathogenic strains.No Full Tex
Author\u27s Response to In My World: Designing Living & Learning Environments for the Young Creating Children’s Environments that Inspire and Instruct by Ro Logrippo
No full textAuthor\u27s Response to In My World: Designing Living & Learning Environments for the Young: Creating Children’s Environments that Inspire and Instruct by Ro Logripp
Ro-Ro verbinding Vuurland met het vasteland van Argentinië
No full textIn het vooronderzoek is voorbereidend werk gedaan voor het ontwerp van de Ro-Ro-haven. In het voor u liggende rapport staat beschreven hoe dit ontwerp verder is uitgewerkt. In het eerste hoofdstuk wordt een inventarisatie gemaakt welk type schip er voor dit specifieke Ro-Ro-vervoer ingezet moet worden. Na de te vervoeren lading in hoofdstuk 3 te hebben besproken wordt de indeling van het schip vastgesteld. Deze indeling moet zodanig zijn dat het aan te vereiste vervoerskapaciteit voldoet. In de daarop volgende hoofdstukken wordt het programma van eisen op nautisch gebied behandeld. Hier komen onderwerpen ter sprake zoals de breedte en vorm van de haventoegang. Binnen de haven zijn korrektie- en stopafstand en de afmetingen van de draaicirkel van groot belang voor de manoeuvreerbaarheid van de schepen. Het enorme getijverschil heeft grote invloed op het havenontwerp. Er is daarom in hoofdstuk 7 een mathematisch model van de getijkromme gemaakt waarmee een voorspelling van de waterstanden kan worden gedaan. Dit is o.a. van nut geweest bij de bepaling van de ligging van de brekerzone en de probabilistische benadering van de noodzakelijke geuldiepte. De golfbrekers moeten de haven bescherming bieden tegen golfaanval vanuit zee. Daarom is aan dit belangrijk element in het projekt veel aandacht besteed. Een interessant aspekt hierbij is ook de bepaling van de kruinhoogte. Het P.I.A.N.C. heeft strenge eisen gesteld aan de golfdoordringing bij Ro-Ro-havens i.v.m. de gevoeligheid van de lading voor bewegingen van het schip. Uitgaande van deze eisen is een diffraktieberekening gemaakt om te onderzoeken in hoeverre het ontwerp voldoet aan de P.I.A.N.C. eisen. Om een goede ladingafhandeling mogelijk te maken is een flexibele pontonkonstruktie ontworpen die bij elke getijwaterstand kan funktioneren. Daar de ponton geen stootbelasting kan opnemen is tussen schip en ponton een remmingwerk gesitueerd. Dit is berekend op een extreme stootbelasting van het Ro-Ro-schip. Tenslotte is een berekening gemaakt van de troskrachten die optreden bij windbelasting op het schip als het ligt afgemeerd.Hydraulic EngineeringCivil Engineering and Geoscience
Development overview of Ro-Ro ships
No full textRazvoj Ro-Ro brodova traje u kontinuitetu već više od 180 godina. Svoj povijesni razvoj započinje u Škotskoj gdje se pojavio prvi trajekt koji prevozi Ro-Ro teret, u ovom slučaju željezničke vagone. Ro-Ro brodovi razvijaju se usporedno s integralnim i multimodalnim prijevozom jer su i oni sami dio ovog tipa transporta. U 60-im godinama prošlog stoljeća dolazi do uspostavljanja velikog broja kratkih linija na području Sjevernog i Baltičkog mora, koje se danas nastoji ponovno oživjeti. Prednosti Ro-Ro brodova u početku su bile vidljive na kraćim relacijama no naknadno ih pokazuju i dugim relacijama. Najniža visina troškova po jedinici tereta u usporedbi sa drugim sustavima kao prvenstvena prednost Ro-Ro tehnologije omogućena je dobrim prekrcajnim normama te se danas uspješno kombinira sa drugim tehnologijama. Isključiva namjena Ro-Ro brodova je prijevoz tereta na kotačima. U uvodnom dijelu rada autor analizira i interpretira te opisuje razvoj Ro-Ro brodova kroz pojedina povijesna razdoblja, a zatim opisuje suvremeni Ro-Ro brod i njegove osnovne karakteristike. U drugom dijelu rada autor provodi analizu prometa Ro-Ro brodova na Jadranu u posljednjih 5 godina. Vezano uz to autor nudi pojedine zaključke i prijedloge. U posljednjem dijelu rada (Zaključak) dana su zaključna razmatranja o temi.The development of Ro-Ro ships has been going on continuously for more than 180 years. Its historical development begun in Scotland where the first ferry carrying Ro-Ro cargo is primarily applied, and in this case railway wagons. Ro-Ro ships are being developed parallel with integrated and multimodal transport because they themselves are part of this type of transportation. In the 1960s, a large number of short lines were established in the North and Baltic Seas, which are now being revived. The advantages of Ro-Ro boats were initially visible on shorter distances, but later they also showed them on long distances. The lowest cost per unit of cargo compared to other systems as a primary advantage of ro - ro technology is provided by good transhipment standards and today is successfully combined with other technologies. The exclusive purpose of Ro-Ro boats is to transport cargo on wheels. In the introductory part of the paper, the author analyzes and interprets and describes the development of Ro-Ro boats through certain historical periods, and then describes the modern Ro-Ro ship and its basic characteristics. In the second part of the paper, the author analyzes the traffic of Ro-Ro boats in the Adriatic sea in the last 5 years. In this regard, the author offers some conclusions and suggestions.
In the last part of the paper (Conclusion), concluding remarks on the topic are given
Direct numerical simulation of weakly spanwise-rotating turbulent plane Couette flow
No full textIn this report, we conduct direct numerical simulations (DNS) of weakly spanwise-rotating plane Couette flows at Reynolds number (here, is the half the wall velocity difference, and is half-channel height). A series of simulations with different rotation numbers ( is constant angular velocity component in the spanwise direction) is carried out to investigate the effect of on the flow statistics. Our results show that the flow statistics are affected by the , and a "critical" rotation number (between and ) is observed, where the kinetic energy of secondary flow contributes about a half of the turbulent kinetic energy, and the mean shear rate at the center line reaches a minimum value. We conjecture that different mechanisms should exist around , and will be investigated further
Multi-criteria evaluation of an alternative diluted seawater RO desalination process incorporating wastewater recycling
No full textDesalinated seawater is often the primary source of drinking water on coastal islands. While seawater reverse-osmosis (SWRO) desalination technology has significantly reduced the energy intensity of the desalination process over the past decade, it is still much higher than that of conventional water treatment technologies. There are also concerns about the potential environmental impacts of SWRO desalination plants because of direct disposal of concentrated brine into the ocean and the high energy demand of the process being predominately met by fossil fuels in off-grid island settings.
This study evaluated the capacity for the dilution desalination process (DDP) to lower energy use and reduce brine disposal in the desalination of seawater. In the DDP, lower salinity water recovered from treated wastewater effluent is used to dilute seawater before it enters the reverse-osmosis (RO) membrane. As such, less energy is required to desalt the (diluted) feedwater. In my study, two DDP processes are assessed: osmotic dilution desalination (ODD) and mixing dilution desalination (MDD). The ODD process involves a hybrid forward osmosis (FO)–RO configuration and the MDD process an ultrafiltration (UF)–RO configuration. In this thesis, these dilution processes will be referred to as simply MDD (UF-RO) and ODD (FO–RO).
Treated wastewater, or secondary effluent (SE), is used as a supplemental water source for reducing salinity in seawater desalination, and pre-treated seawater from a seawater treatment plant is used as the feedwater in the dilution process. In the first configuration, the FO−RO hybrid (applying the ODD process), pre-treated SE from the wastewater stream is used to dilute seawater before RO.
In the second configuration, UF is integrated with an RO section. The same impaired water from the sewage plant diffuses through a UF membrane for pre-treatment before moving through the RO membrane. As such, diluted seawater with lower salinity is prepared for SWRO desalination. In both configurations, less energy is required for desalination and safe water is delivered for direct potable reuse (DPR).
Recent reviews on the development of the FO process have highlighted mass transfer limitations, internal concentration polarisation (ICP), external concentration polarisation, fouling and solute rejection flux as key challenges leading to low water flux in FO membranes. UF achieves higher water flux, as the driving force of permeate water is hydraulic pressure, in contrast to the FO membrane process, which relies on natural osmotic pressure. Moreover, the fouling and ICP problems are resolved by the UF process due to the bigger mesh size of the membrane. However, UF uses a hydraulic energy-dependent membrane and requires more power than is required for FO membranes, which could be considered an environmental drawback. Using two successive dense membrane processes in hybrid ODD (FO–RO) configuration could increase consumer confidence in wastewater use in seawater desalination.
This study undertook a comprehensive assessment of wastewater reuse combined with seawater desalination in two DDPs. Prior to undertaking this assessment, the benefits, advantages and challenges of alternative dilution methods (e.g., UF) and knowledge gaps were discussed. The key factors considered in the multi-criteria evaluation were technical performance, economic feasibility, environmental impacts, and health and quality.Thesis (PhD Doctorate)Doctor of Philosophy (PhD)School of Eng & Built EnvScience, Environment, Engineering and TechnologyFull Tex
Development of an Auto-Trim Control System for Ro-Ro Ship Carrying Heavy Cargoes
No full textIn Ro-Ro ship carrying heavy cargoes, it is very important to maintain a certain level of aft draft and the proper trim through the entire loading or discharging process. Some kinds of manual ballast control system have been generally applied so far to this practice in Ro-Ro ship. However, there is need to develop a so-called Auto-Trim Control System using some computer technology to improve the operation of those existing systems.
This paper aims at developing an Auto-Trim Control System especially for Ro-Ro ship carrying such heavy cargoes including hot coils and steel plates. The author carried out some systems analysis and design for developing the system by examining and reflecting the practices of the entire loading and discharging process.
Then a user-friendly Auto-Trim Control System has been built by interfacing the Valve Remote Control system and Tank Level & Draft Measuring system with itself. The author also provides some excellent results on the performance of the system by reporting the records of installing the system on board 4 Ro-Ro ships.Abstract
제 1 장 서론 = 1
1.1 연구의 배경 = 1
1.2 연구의 목적 = 2
제 2 장 시스템의 개요 = 3
2.1 중량화물 선적 Ro-Ro 선 하역 작업의 기본개념 = 3
2.2 Auto-Trim Control System의 기본개념 = 7
2.3 시스템 구성도 = 10
제 3 장 선미흘수 및 트림 제어 알고리듬의 개발 = 11
3.1 탱크 배치도 = 11
3.2 탱크 배정 우선순위 = 11
3.3 탱크 선택 규칙 = 12
제 4 장 Auto-trim Control System 개발 = 15
4.1 시스템 소프트웨어 구성 = 15
4.2 시스템 설계 = 16
4.3 밸브 및 펌프 작동 절차 = 21
4.4 시스템 구현 = 37
제 5 장 프로그램 실행 예 = 42
5.1 통신상태 표시줄 = 42
5.2 선박상태 표시줄 = 44
5.3 프로그램 작동 = 45
제 6 장 결론 = 58
참고문헌 = 6
High silica concentration in RO concentrate
No full textSilica scaling is one of the major scaling challenges in Reverse Osmosis (RO). The safe operation practice is to keep the silica concentration below 150 mg/L in RO concentrate. This study addresses the effects of divalent cations such as calcium and magnesium on silica scaling in a seawater RO installation used as a pretreatment to Eutectic Freeze Crystallisation (EFC). Results showed that in the absence of antiscalant and divalent cations a sustained silica concentration of approximately 280 mg/L in concentrate is possible without declining membrane permeability. At a higher concentration of divalent cations, the membrane permeability decreased. Membrane autopsy and analysing destructed membrane showed a relatively low magnesium and a high calcium concentration on the membrane after adding divalent ions into the solutions. It is concluded that in absence of divalent cations and without antiscalant the limits of 150 mg/L silica can be extended to 280 mg/L for 6–8 h.Sanitary Engineerin
RO(C₂)-graded Stable Stems and Equivariant Framed Bordism
No full textThe purpose of this dissertation is to prove fundamental relations in the -graded stable equivariant homotopy groups of spheres using geometric methods. The main tool we use is a singular version of the Pontryagin-Thom isomorphism which holds in the equivariant setting. Our work then consists of writing down explicit bordisms between manifold representatives of homotopy classes. Selected relations include , , and where and are equivariant Hopf maps, is a unit in , and is the generator of . We also completely characterize the periodic portion of the topological zero-stem using singular manifold representatives which are the products equipped with various -actions. While we focus on , most of the theory we develop applies to -graded homotopy groups for arbitrary finite groups
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