bluuebunny/crossref_metadata_2025 huggingface dataset:
Deep Generate Residual Similar Feature Networks for Image Super-Resolution
Authors: Li Xian , Zhang Jiahuan , Wang Minjie , Xu Gang
Published: September 2019

In this paper, Driven by advanced convolutional neural networks, we present a deep generate residual similar feature networks to improve super-resolution performance. Many researches have found that many CNN network training of SR requires skill and computing equipment. The input low-resolution features and CNN intermediate features contain rich similar feature maps. The different upscaling factor is used for needing the different model, which increase computational complexity. For the problem raised above, we proposed the generate residual feature (GRF) module to generate more high-frequency information in the residual feature. Each generated residual structure contains the short skip connection and long skip connection. Furthermore, we extract the similar feature in the residual feature by considering the interrelation among residual feature. Qualitative and quantitative assessments on benchmark datasets shows that we use different methods to achieve the same effect as best results of SR, while we make the network light weighted. Meanwhile, Our experiments shows that the pedestrian detection in the monitoring scene has achieved good results.
Research on Parameter Identification Algorithm of Updraft Based on Energy Recursion of Unmanned Aerial Vehicle
Authors: Zhang Ge , Tian Yingxin , Xi Boqi , Yi Guoxing , Xu Zeyuan
Published: September 2019

In this paper, the problem of UAV utilizing updraft energy near flight path is modeled, simulated and analyzed. Firstly, a simplified updraft model is established according to the characteristics of updraft. Then, according to the energy trend of UAV in the updraft, the recursive algorithm of UAV energy and the information acquisition model of UAV in the updraft are designed. Based on Nelder-Mead minimum search algorithm, an updraft parameter identification scheme is designed and simulated. It can be concluded that according to the above design scheme, UAV can basically identify the parameters of the updraft region, and achieve a certain identification accuracy, which provides a reference for future research.
Research on Power Control Strategy for 35kV Medium Voltage Transformerless PCS
Authors: Yang Bo , Li Guanjun , Li Dan , Yu Haojie
Published: September 2019

The continuous growing generating capacity of new energy power has brought more and more serious impact on the stability of electrical power system. As an important method to compensate the fluctuating power of new energy plant, highly efficient large-scale power storage system has played a more and more important role in helping stabilizing electrical power system. In this paper, a topological structure of 35kV transformerless power storage system is designed, and an active and reactive decoupling control system against this system is proposed. Concerning the application scenario of primary frequency regulation, an active support frequency response control technology for power grid with changing the droop coefficients based on three response modes is put forward. Finally, the control strategy designed is simulated and verified by using PSCAD system. The simulation result shows that the system and control strategy can do very well in active support frequency response control for power grid.
Research on Shape Optimization of Marine Magnetometer Based on Adjoint Method
Authors: Hu Xiaomei , Zhang Yiqi , Chai Jianfei , Ali Mubarak
Published: September 2019

There are many magnetic objects underwater, such as pipelines/pipelines, optical cables, cables, etc. Ocean magnetometer can locate and identify them. It is very important for the detection of underwater magnetic objects whether the marine magnetometer can be in a relatively stable state when it is moving underwater. Accordingly, shape optimization of marine magnetometer based on adjoint method is proposed. Firstly, a fluid region model is established to simulate the underwater motion of the marine magnetometer, and pressure and velocity maps are obtained. Then, the shape of the marine magnetometer is optimized by adjoint optimization technology. The simulation results show that the shape optimization of the ocean magnetometer makes the drag reduction rates of the front of the transponder part, the towed part and the side of the probe part become 40%, 35% and 27%, and the effect of optimization is obvious.
Target Threat Assessment Based on Dynamic Bayesian Network
Authors: Wang Xin , Zuo Jialiang , Yang Rennong , Zhang Zhenxing , Yue Longfei , Liu Huiliang
Published: September 2019

Conventional threat assessment model based on Bayesian Network is a reasoning process in static environment, which is difficult to deal with a large number of broken air combat data in a complex dynamic battlefield environment. Motivated by this fact, a Dynamic Bayesian Network-based threat assessment model is established, and a theoretical method based on Expectation Maximization to deal with missing data is proposed. Finally, simulations are presented to verify the effectiveness of the proposed structure.
Research on Optimization of Association Rules Mining Algorithm
Authors: Li Ningning , Lu Zhaoxia
Published: September 2019

The association rules mining algorithm is always one of the specialists most concerned topics in the research of database knowledge. It is widely used in many fields in society. This article is based on association rule mining algorithm to put forward the relevant strategies for the majorization to make the mining algorithm get better application. With the development of the society, social information becomes richer and richer, people also become more and more interested in the unknown world. Sustainably improve the automation and intelligentization of the tools for processing information can continually improve the abilities in many ways and get more useful information from the huge database. So the appearance of the data mining makes it possible. It can fetch some hidden, unknown and useful information and knowledge from the huge practical application data. And the association rule is a main mode in research of data mining. It can fetch target data by finding the dependency between fields of a given condition from different data fields. As a result, the optimization of association rules mining algorithm is of quite importance in fetching target data.
Design and Implement of a General Zone Controller for Intelligent Building Platform System
Authors: Shi Long , Zhang Yewei , Li Jing
Published: September 2019

There are several problems of traditional building monitoring and management system, such as separation and isolation of sub-systems, lack of linkage control, low compatibility, difficulties in extending, etc. A design of intelligent building platform system architecture, which is compatible with existing building systems, has been put forward after the research of intelligent building technology. Combined with the requirements of modern intelligent building, a general zone controller with powerful processing capabilities, rich peripheral interface, multiple communication protocol and communication protocol has been designed and impleted. The zone controller can support the connection and linkage of various sub-systems, devices and sensors in different zone of the intelligent building. An intelligent conference management system of intelligent building system has been realized based on the zone controller.
Research on Image Processing Methods in Pavement Crack Extraction
Authors: Zhang Zhihua , Zhang Xinxiu , Yang Shuwen , Yang Jun
Published: September 2019

Since the acquired road images are affected by weather and lighting factors, a large amount of noise information is contained. Therefore, it is necessary to denoise the image. Based on the acquired large number of images, the best method is selected through comparison to three image compression methods; after compressed, the image gray-scale processing method based on YUV is selected through comparison; then, the image enhancement processing method based on the frequency domain transformation is selected, and the image denoising process is performed by comparing three denoising methods, the best effect is for median filter; finally, the two image stretching methods are compared, by using the custom function adjstra method, the better image stretching effect can be achieved. So, the image processing method selected by the invention can enlarge the useful information of the image more effectively, and simultaneously, the influence of image noise is greatly reduced.
Residual Cigarette Recycle System Spectrum Switching Based on Markov Model
Authors: Sun Shunkai , Li Jie , Xu Qi , Zhu Jiule , Cao Weilin , Chen Haitao , Liu Ruidong , Hu Wangdi
Published: September 2019

In the process of communication of residual cigarette recycle system, due to the residual cigarette recycling bin WIFI switch with the signal strength, signal quality, distance of WIFI and other reasons. In order to keep the residual cigarette recycling bin in a non-inductive switching state, WIFI needs to adopt seamless Switching technology [1]. In which cognitive radio automatic networking (CRAN) is one of the core technologies, in order to suppress cognitive users from interfering with authorized users, it is necessary to reduce WIFI switching times as much as possible. Advance a cognitive wireless dynamic WIFI switching method based on detection of the WIFI chanel idle time (PWCIT). The theory is based on a known-state sequence hidden Markov [2] model (KSS-HMM). The selection method of the alternative WIFI is given, and the optimal channel is selected for data transmission by comparing the date transmission throughput of each candidate WIFI. The simulation results show that compared with the traditional channel selection method and the random channel [3] selection, the method can significantly reduce the number of WIFI handovers and improve the throughput of cognitive [4] users.
The Vertex Degree Distance of One Vertex Union of Two Cycles
Authors: Guo Haili
Published: September 2019

One vertex union of two cycles is a kind of multi-cycle graphs. In this paper, the vertex degree distances of one vertex union of two cycles are calculated, and on this basis, the maximum and minimum of vertex degree distances are studied. The results show that the maximum vertex degree distances of one vertex union of two cycles is at the common intersection vertex and the minimum at the adjacent vertices of common intersection vertex.
An Improved Particle Swarm Optimization Based on Hormone Modulation Mechanism
Authors: Xiao Chuncai
Published: September 2019

The manufacture of polyacrylonitrile carbon fiber (PCF) contains a group of workshop technologies with very complexity. A pivotal technology is the coagulation of the PCN in production of fiber which has a great many arguments connecting with one another. In this paper, an PID neural networkregulate strategy with improved particle swarm optimization (PIDNNHPSO) on account of the endocrine hormone regulate theory of human body is presented, and used to the coagulation tank of PCF manufacture. Three crucial arguments including liquid high, temperature, concentration of water are extracted. Experimental consequences reveal that the PIDNNHPSO can promptly response to the alternating quantity of regulate arguments, perfectly cut down the coupling effect and make reposeful adjustion without fluctuation, which has a exceed property than traditional regulate programmes.
Virtual Hospital with Real-Time Image Diagnosis
Authors: Mihertie Habtamu Demeke , Gao Ying
Published: September 2019

Recently, deep learning models such as deep convolutional neural networks have shown great success in different imaging tasks in general and in detection of diabetic retinopathy in particular. An automated detection system is undoubtedly a great help for the screening stage of diabetic retinopathy for further treatment to reduce the burden on the public health system. In this paper, a general framework for automated detection virtual environment is developed as a virtual hospital using a convolutional neural network (CNN) approach as imaging end. Image classification is done in two stages. The best model being 87.12% accurate for the first stage on more than 53000 images which is better than previous works tested only on very less amount of test data. Using this model, a standalone application is generated with extra features for user interaction to be used by the patient in the virtual hospital when he presses a key on the keyboard.
Guided inquiry model based on scientific approach to science learning of the students of SMPK Stella Maris Biudukfoho
Authors: Tabun Y F , Sunarno W , Sukarmin
Published: September 2019

This study aimed to determine the science learning outcomes of students in the aspect of cognitive, affective and psychomotor using a guided inquiry model based on a scientific approach. This study is quasi-experiment with nonequivalent control group design. The population is the whole students of Stella Maris Biudukfoho Chatolic Junior High School (SMPK) at grade eight in the Academic Year of 2018/2019. The sample consists of two classes taken by cluster random sampling technique, namely class VIII A as the experimental class and class VIII B as the control class. Data collecting tools namely tests, questionnaires and observation sheets were used in this study. Data analysis of students’ learning outcomes were done using Independent Samples t-test. The results of the three aspects of learning outcomes namely aspects of knowledge, attitudes and skills indicated that the p-value < 0.05 so that H0 is rejected and Ha is accepted. Thus, there were differences in learning outcomes of students who were given learning method using guided inquiry with students using who were given conventional learning. However, the results from data analysis, p-value of knowledge aspect is 0.000, p-value of attitudes aspect is 0.043 and p-value of skills aspects is 0.001.
Influence of physics problem-solving ability through the project based learning towards vocational high school students’ learning outcomes
Authors: Retno N H D , Sunarno W , Marzuki A
Published: September 2019

Physics, an adaptive subject in SMK, is the basis and prerequisite for productive and applicable material, so it needs to be emphasized on problem solving approaches. This study aimed to determine the influence of learning methods based on the problem solving ability on learning outcomes. The intended learning outcomes are cognitive learning outcomes and the learning method used is project based learning. The type of research was quasi-experiment. The population in this study were the 10th grade students of SMK Negeri 5 Surakarta in the 2018/2019 academic year which consisted of 7 majors with 22 classes. The sample of this study were 2 classes from the Mechanical Engineering department, each of which amounted to 35 students. The instrument used in this study consist of 20 multiple choice questions and 5 essay question of the Physics problem solving abilities. Data were analysed using normality test, homogeneity test and hypothesis testing with analysis of variance techniques (ANOVA). Based on the results of the study it was found that the influence of the interaction between learning method and problem solving ability on cognitive learning outcomes showed sig 0.043 ≤ 0.05. It can thus be concluded that there was an influence of the interaction of the learning model with the problem solving ability with cognitive learning outcomes. Therefore project based learning methods can be used as an alternative for teachers in carrying out their learning to create an active learning atmosphere and enhance students’ ability to understand physics problems.
Fractionation and determination of phenolic and flavonoid compound from Moringa oleifera leaves
Authors: Martono Y , Yanuarsih F F , Aminu N R , Muninggar J
Published: September 2019

Moringa oleiferais one of the nutrient-dense multipurpose plants that grows in Indonesia.M. oleiferaleaf extract contains many phenolic compounds and flavonoids, one of them is quercetin compounds. In this study, total phenolic, total flavonoid, and quercetin compounds were determined based on their fraction as free phenolic acids (FPA), phenolic acid ester (PAE), and phenolic acid glycosides (PAG) which separated by phenolic acid fractionation methods. Fractionation method was done by liquid-liquid extraction. Total Phenolic compounds and flavonoid were determined using spectrophotometric UV-Vis. The concentration of quercetin was determined using High-Performance Liquid Chromatography (HPLC). Total phenolics in the crude extract (CE), FPA, PAE, and PAG fractions respectively were 50.2042; 5.7963; 1.5260; and 0.0617 mg/g GAE. The total flavonoids in the CE, FPA, PAE, and PAG fractions were 25.6627; 1.7207; 1.0510; and 0.2843 mg/g QE. The quercetin compounds in the CE, FPA, PAE, and PAG fractions were 1.7123; 1.9607; 0.1921; and 0.5067 μg/g.Moringa oleiferais potential natural sources for phenolic and flavonoid, particularly of quercetin.
Analyzing the shape of photoacoustic signal on audible frequency modulation
Authors: Setiawan A , Rondonuwu F S , Setiaji F D
Published: September 2019

This paper reports the result of measurement and analysis of the shape of photoacoustic signal emitted from an object which is a piece of carbon paper, excited by a diode laser beam, which modulated by a square wave signal at audible frequency, so that acoustic measurement can be done easily and inexpensive. Here PC Real Time Audio Spectrum Analyser (RTA 168) from Virtins Technology is used to measure and record the acoustic signal. Three modulation frequencies were chosen which were 5.045, 9.576 and 14.816 Hz, all with 50% of duty cycle. The result showed that the fundamental frequency of photoacoustic signal fit to modulated laser’s signal. Measurement at 5,045Hz, as an example, showed that the shape of the photoacoustic signal fit to the model with average error of 5%. The absorbtion coefficient of carbon paper could also be calculated as μa
=1.49cm−1.
Shear Strength Characteristics of Coastal Soil Treated with Sodium Silicate
Authors: Erica Amaludin Adriana , Teo Twan Ann Melvin , Radzif Taharin Mohammad , Dullah Salinah
Published: September 2019

In recent times, rapid developments near coastal areas are gaining attraction and attention from industry players. This necessitates further understanding of soil behavior found in these areas. Soil stabilization can further enhance the physical and engineering characteristics of soils used for development purposes. For this study, a series of laboratory tests were conducted to determine the potential of Sodium Silicate (TX-85), a liquid-type chemical soil stabilizer, to improve the properties of coastal soil obtained in Kota Kinabalu, Sabah. The soil samples were subjected to a series of laboratory tests, which includes the pH and Unconfined Compression Strength (UCS). The dosages of Sodium Silicate mixed with the soil were 4, 5, and 7% by soil sample weight, with curing intervals of 3 hours, 24 hours and 48 hours, respectively. The optimal dosage of Sodium Silicate observed in this study is 4%, at 48 hours curing period. This combination of stabilizer dosage and curing period produced the highest strength increment, where the UCS value increased by 90.3%, from 262.1 kPa to 498.8 kPa.
Dimensions of Tenants’ Office Leasing Behaviours: An Introductory Study
Authors: Kim Sumin , Lim Benson T.H.
Published: September 2019

The greenness of office buildings is becoming a more important issue as it contributes to the sustainability of the building sector. Moreover, by leasing greener offices, tenants can be benefitted by the improved indoor environmental quality and better corporate branding attributed to its positive image. These benefits, however, often come with relatively expensive prices that tenants need to pay. Nevertheless, the sources of the price premium have not been fully explored especially from the aspect of tenants’ leasing behaviours. To address this, a questionnaire survey was conducted. Then, exploratory and confirmatory factor analysis were performed to identify the underlying dimensions of tenants’ leasing behaviours and to ensure their reliability and validity. The results show that tenants’ office leasing behaviours must be explained by several dimensions. Also, it is found that the obtained results have a sufficient reliability and validity. These allow proceeding to the next stage of the research to explain if and to what extent the greenness level of tenants’ offices and the rents they pay are influenced by various motivational variables based on the established analytical model.
Conceptualising eco-innovation practices in contractor firms – the dynamic capability approaches
Authors: Sarah Mat Isa Siti , Zainul Abidin Nazirah , Yahaya Izyan
Published: September 2019

The world has witnessed extreme environmental deterioration over the past few decades due to rapid development in urban areas and unsustainable way of past construction. Recently, eco-innovation (EI) has increasingly been accepted as the solution to major environmental problems. EI involves new or modified processes, techniques, products, systems, and services that can satisfy human needs and provide quality of life whilst significantly decreases environmental impacts. In addition, EI revolutionary path to improve contractor firms’ competitiveness and sustaining business endeavour. Thus, the aim of this paper is to develop EI framework practices in contractor firms. Unfortunately, to be eco-innovative, the contractor firms need to strengthen their green knowledge, technology and resources as well as to develop their capabilities and strategies faster than their rivals. They also need to absorb and capitalise any external opportunities for their own advantages. Therefore, this study adopts dynamic capability theory to investigate a firm’s ability to integrate, build and reconfigure its competences and resources to accomplish the environmental goal in its business strategy. The outcome of this paper could provide clear directions of EI practices by means of dynamic capability theory in demonstrating how contractor firms can adapt to changing current industry conditions to remain competitive.
Compressive Strength and Infiltration Characteristic of Pervious Concrete Using Recycled Concrete Aggregate
Authors: Aishah Abd Rahman Nurul , Aiman Muhamad Shah Muhammad , Safwan Muhamad Noor , Amzari Yaccob Ahmad , Zardasti Libriati
Published: September 2019

In construction industry, rapid development will increase the demand versus supply which leads to increasing the production of construction waste. Recycle Concrete Aggregate (RCA) was proposed as the one of the component in the pervious concrete for sustainability in the construction industry to reduce the wastage. The pervious concrete was function as a medium to allow the water penetrate through porosity of the concrete and avoiding water from pooling at the surface. Therefore, this study is conducted to investigate the properties of the pervious concrete by infiltration test and compression strength test using Recycle Concrete Aggregate (RCA) and Natural Aggregate (NA) as the main composition. The cement aggregate ratio of 1:3 and 1:5 were choosing as variable to produce the workability pervious concrete that similar to conventional concrete. The replacement of NA with RCA is likely a viable option for structural use.
Screw Rotors with Partial Length Contact.
Authors: Davey D W
Published: September 2019

Tribology theory suggests manufacturing screw rotors with partial helical contact along the longitudinal axis of the intermeshing rotors may significantly influence their lubrication characteristics. This paper considers the theoretical effects of using this geometry feature for multiphase flow machines. Modelling of machines that include partial contact along with other relevant aspects such as oil port location, has further been investigated using ANSYS CFX and some results of these simulations are presented and discussed.
Analysis of rolling bearing power loss models for twin screw oil injected compressor
Authors: Abdan S , Stosic N , Kovacevic A , Smith I , Asati N
Published: September 2019

The mechanical losses inside a screw compressor limit the performance of the compressor in terms of efficiency. These losses arise due to relative motion between elements inside the screw compressor. The estimation of mechanical losses predicted in the literature is around 10-15% of the total shaft power. One of the elements which contribute significantly to these losses is rolling element bearings. There are numerous mathematical models available which predict power losses in the rolling bearings.

The objective of this paper is to study different models to predict power loss for rolling bearings and to predict the power losses for the bearings used for oil injected, twin screw compressor. A comparison between different power loss models for different operating conditions of compressor is also presented in this paper and results of analysis are compared with available experimental observations. The analysis helps to determine suitable power loss model for different operating conditions and more realistic predictions of the power losses. This allows designers for more accurate estimation of the performance of screw compressors.
Experimental Investigation of a Mechanically Assisted Suction Reed Valve in a Small Hermetic Reciprocating Compressor
Authors: Egger A , Almbauer R , Dür L , Hopfgartner J , Zuber B , Stangl S
Published: September 2019

Reed valves are widely used in hermetic reciprocating compressors and are responsible for a major share of thermodynamic losses. In particular, the suction valve movement of a hermetic reciprocating compressor contains a potential for further improvement. The self-actuated valve is opened only by the pressure difference created by the moving piston, which leads to a characteristic flutter. Furthermore, the suction valve is usually preloaded in order to close properly before the compression phase, causing additional flow resistance.

In this work a mechanically assisted suction valve is experimentally investigated. A mechanically actuated spring element generates an additional force acting on the conventional suction reed valve. This force leads to a completely different valve motion. While a conventional reed valve motion is characterized by several opening-and closing periods during one suction phase, the mechanically assisted valve remains open during the whole suction phase. Furthermore, the maximum impact velocity of the valve can be reduced significantly. Thus, not only the suction losses but also the valve stress can be reduced.

To investigate the mechanically assisted suction valve, a conventional small capacity hermetic reciprocating compressor is fitted with measurement equipment and additional components for the mechanical valve actuation. Preliminary investigations are made without the hermetic shell to find an appropriate design. Finally, measurement results of the compressor running at steady-state conditions on a calorimeter test bench (R600a) show significant improvements of the coefficient of performance (COP) at different rotational speeds and operating conditions.
Outsourcing in the Compressed Air Sector – Financial Opportunities in Industry
Authors: Vittorini Diego , Cipollone Roberto
Published: September 2019

The compressed air sector is currently responsible for up to 10% world-wide overall industry electricity consumption, 30% of which ascribable to the compressor technology alone. Such a datum makes the saving potential from a proper compressor selection (30-35% overall consumption) as appealing as those associated with other energy measures and in line with the 20-20-20 timeline. Plus, every electricity saving on the compressor virtually corresponds to an income from selling Energy Saving Certificates (usually referenced as White Certificates) and CO2 quotas from avoided emissions on dedicated markets, which can eventually reduce the payback time of the additional investment. Outsourcing in the CAS is addressed as the most effective alternative to efficiency ownership and its development is supported by the common perception of the compressed air as a utility, analogously to electricity and thermal energy. An in-depth net present value analysis is performed on market compressors for industrial purposes, based on the environmental market model, the electricity cost and compressors market policy in the average European context. In addition to the financial advantage from White Certificates and Carbon markets, the outsourcing always benefits from the lower investment cost on the compressor and the higher compressors efficiency: this results in lower sale prices for the cubic meter of compressed air, with little or no difference among different machine types. The relative importance of energy and investment-related costs is assessed as well. The outsourcing allows a m3 cost reduction with respect to the purchase of new compressors in the 15-20% range, dependently on the machine size and operation regime.
Characterization of wire mesh structure for coalescing oil separation
Authors: Xu Jiu , Hrnjak Pega
Published: September 2019

Oil separation is commonly needed in air conditioning or refrigeration systems to reduce the oil circulation rate and keep the oil inside the compressor. For compactness, the oil separation structure integrated into the compressor is more and more popular than traditional external oil separator. This paper presents coalescence, one of the basic mechanisms of droplet separation, studied by quantitative flow visualization and measurements. The misty oil flow through separator is visualized by a high-speed camera and analyzed quantitatively. Oil droplet size and its distribution are determined by video processing. Important flow details are revealed, including oil droplet collision, oil droplet coalescence, oil film breakup and re-entrainment. Separation efficiency is determined as the ratio between drained and incoming oil mass flow rate. Pressure drop is also measured since it is a cost due to separation structures.
Optimization of a three spool axial compressor to increase the efficiency of a gas turbine engine
Authors: Marchukov Evgenii , Egorov Igor , Popov Grigorii , Baturin Oleg , Goriachkin Evgenii , Novikova Yulia
Published: September 2019

The paper provides a description of the algorithm, an example of a specific task, and the results of the optimization of a 15-stage three-spool compressor for a ground-based GTU by the efficiency criteria of the engine. It can be performed by using the proposed algorithm to find such a compressor configuration that will be not just the optimum compressor, but the best option for working as part of the engine under the specified operating conditions and with various types of required restrictions. Using the proposed algorithm, varying only the stagger angles of the profiles, the authors managed to find a way to increase the overall efficiency of the NK-36ST engine by 0.43%. Obviously, it is possible to achieve a more impressive result and at the same time to increase reliability, reduce the weight and cost of the engine by applying more complex models by changing the shape of the blade profiles.
Control and Commissioning of a Hot Gas Bypass Compressor Load Stand for Testing Light-Commercial Compressors on Low-GWP Refrigerants
Authors: Singleton Jake , Schmidt Drew , Bradshaw Craig R.
Published: September 2019

Because of changing efficiency standards for HVAC&R equipment, hydrofluorocar-bon refrigerants such as R134a and R410A are in the process of being phased out because of their high Global Warming Potential (GWP). Many low-GWP refrigerants, such as R1234yf, R1234ze(E), R1234ze(D), R32, and several blends of these, are being considered as replace-ments. This creates a need for design changes to compressors. Recent work by Schmidt et al. (2018) presented a hot-gas bypass compressor load stand constructed at Oklahoma State University to facilitate testing of compressors with their new design changes.

The load stand has a design capacity range of 10-80 tons. This wide spectrum of testing conditions necessitates a comprehensive controls package to maintain stability and control over the simulated operating condition. This controls package was designed in LabVIEW and allows independent control over the compressor suction pressure and temperature and the discharge pressure using PI controllers. The controllers operate to both set the desired operating condition as well as minimize the variation of the parameters with time (i.e. random uncertainty).

A series of commissioning tests were performed to validate the stand operation and performance metric measurements using a 40 ton scroll compressor. The initial results suggested that appropriately balanced cooling water flow and appropriately tuned controllers are critical to minimize random uncertainty of the data. Without appropriate tuning or cooling water control the load stand was unstable. Adjusting the water flow provided stability but yielded random uncertainty of 0.014% compared with both water control and appropriately tuned controller which yielded random uncertainty of 0.0041%.
A new non-destructive method for fault diagnosis of reciprocating compressor by measuring the piston rod strain
Authors: Li Xueying , Peng Xueyuan
Published: September 2019

As an established method to analyse the thermodynamic process inside the cylinder, the p-V diagram can identify typical faults such as leakages through the sealing rings and self-acting valves, loosening and fluttering of the vales, etc. However, the installation of the pressure sensor within the cylinder for recording the p-V diagram may lead to degradation of the cylinder integrity, and hereby potential leakage and lowered strength of the cylinder. This paper presents a new non-destructive method for fault diagnosis of the reciprocating compressor by measuring the piston rod strain, from which the p-V diagram was transformed. An algorithm for reconstruction of the p-V diagram was proposed based on the key feature points on the piston rod load curve that reflect the opening and closing events of the compressor valves. The reconstruction method was validated by comparing the calculated p-V diagrams with the experimental results. The reconstructed p-V diagrams were further used for fault diagnosis of the reciprocating compressors, with which the acoustic emission method was integrated. The results show that this method can easily monitor the working conditions and identify whether and where leakage, fluttering and delayed closing of the valves occur, which indicates that this method can be utilized as a powerful tool of non-destructive condition monitoring and fault diagnosis of the reciprocating compressors.
Assessment of simplifying hypotheses adopted for valve leakage modeling
Authors: De Luca L G M , Silva E , Deschamps C J
Published: September 2019

The reed-type valves employed in refrigeration compressors must provide adequate sealing when closed to avoid leakage of gas between the compression chamber and the suction and discharge chambers. Recent studies show that valve leakage can considerably affect the performance of the small reciprocating compressors used for domestic refrigeration. The present paper reports an investigation on the adequacy of simplifying the hypothesis adopted in the simulation models of valve leakage. The results indicate that the transient effects related to both the valve deflection and fluid flow are negligible. Also, the ideal gas formulation was found suitable in some operating conditions found in domestic refrigeration. On the other hand, leakage was found to be overpredicted by almost 20% when the reed valve geometry was simplified to a circular plate in order to reduce the computational processing cost.
The roticulating concept air compressor: experimental and numerical investigation
Authors: Zhang Y , Madamedon M , Copeland C , Fenton J P , Subert J , Hinchliffe K , Arbon I M , Leefe S
Published: September 2019

This paper documents the first prototype tests of the FeTu bare-shaft oil-free air compressor, conducted over a one-year study at the University of Bath, with funding support from Innovate UK. Giving feasibility to the concept and to provide an initial indicator of its performance, in terms of pressure capability, isentropic efficiency and specific power demand as an oil-free air compressor.

A range of 6 units in total were validated on a continuous flow test-rig, with variations on internal sealing, internal clearance, and Non-Return Valve (NRV) settings, to assess their impact on volumetric efficiency, in pursuit of an optimal design.

Tests covered a speed range of 100 rpm-1500 rpm and reached discharge pressures up to 6 barg, results indicated that the compressor can maintain a 50% torque-based efficiency between a pressure ratio (PR) of 1.5 to 2.8. Tests reveal low compressed gas temperature of 125ºC at 2.8PR, which gave rise to a high isentropic efficiency of over 80%, therefore specific power was adopted as the main Key Performance Indicator (KPI).
The analysis of energy conservation employed in the control of linear compressor
Authors: Tang Mingsheng , Zou Huiming , Li Xuan , Tian Changqing
Published: September 2019

Linear compressors have received more and more attention for their compact structure and high efficiency. They are highly sensitive to the working condition, thus the control system is essential to ensure linear compressors are able to operate reliably and efficiently. Operating in a resonant state would improve linear compressor efficiency, while the natural frequency is also sensitive to the operating condition. This paper proposes the analysis of energy transfer process during linear compressor operation. Compared with force analysis, energy analysis uses the electromechanical analogy to show the energy conversion from electrical energy into mechanical energy during linear compressor operation. The principle for the control to achieve high efficiency is proposed and verified in a refrigeration system. The result shows it is practical and reliable to applied energy analysis in the control of linear compressor to achieve highly efficient driving.
Optimization of Suction Chamber Structure in a Scroll Refrigeration Compressor
Authors: Shuaihui SUN , Xianwen WANG , Pengcheng GUO , Xiaobo ZHENG , Jianguo YAN
Published: September 2019

In order to improve the suction performance of the scroll compressors, five modification models are proposed by reducing or enlarging the area of the suction flow passage based on a scroll refrigeration compressor. The three-dimensional numerical simulation model is established using the commercial software PumpLinx to calculate the flow field and the performance of every modified model. The comparison and analyses has been done based on the simulation results. The results indicated that the enlargement of the suction passage only improve the volumetric efficiency a little while the shrink of the suction passage can improve it effectively. The mass flow rate pulsation when the modification angle is 270° is much higher than that of the original model, but it decreases with the modification angle. As the modification angle increases, the volume of inner suction passage and the back flow rate from the inner suction passage decrease and less fluid from suction chamber 2 flows back to the suction port, so the average mass flow rate increases and the mass flow rate pulsation decreases. The Model 5 has the maximum volumetric efficiency and lower mass flow pulsation, but the tangential and radial forces on the orbiting scroll are the highest.
Design Method of Offsetting the Orbiting Scroll and Its Influence on the Self-Rotation Characteristics of the Orbiting Scroll
Authors: Zhang Shuai , Wu Jianhua
Published: September 2019

In order to reduce the diameter of compressor casing of the automotive scroll compressor, the orbiting scroll is sometimes offset along a certain direction. This paper summarizes the method of offsetting the orbiting scroll, and analyses the influence of the offset amount on the self-rotation characteristics of the orbiting scroll. The theoretical calculation results show that a larger offset amount is beneficial to increase the stroke volume, however it is easy to make the orbiting scroll rotate around its driving center in the negative direction which would cause an impact on the scroll wrap and the anti-rotation mechanism. At last, this paper affords some advices in how to offset the orbiting scroll.
Near-field acoustic levitation and applications to bearings: a critical review
Authors: Shi Minghui , Feng Kai , Hu Junhui , Zhu Jiang , Cui Hailong
Published: September 2019

The importance to industry of non-contact bearings is growing rapidly as the demand for high-speed and high-precision manufacturing equipment increases. As a recently developed non-contact technology, near-field acoustic levitation (NFAL) has drawn much attention for the advantages it offers, including no requirement for an external pressurized air supply, its compact structure, and its ability to adapt to its environment. In this paper, the working mechanism of NFAL is introduced in detail and compared to all existing non-contact technologies to demonstrate its versatility and potential for practical applications in industry. The fundamental theory of NFAL, including gas film lubrication theory and acoustic radiation pressure theory is presented. Then, the current state-of-the-art of the design and development of squeeze film air bearings based on NFAL is reviewed. Finally, future trends and obstacles to more widespread use are discussed.
Antithrombotic therapy in patients with atrial fibrillation undergoing coronary artery stenting
Authors: Lacoste Jordan L , Hansen Cory L
Published: September 2019

Purpose

Updates to the primary literature and clinical practice guidelines on use of antithrombotic combinations for patients with atrial fibrillation (AF) undergoing percutaneous coronary intervention (PCI) and stenting are reviewed.

Up to 8% of patients undergoing PCI have AF and thus require both antiplatelet and anticoagulation therapies, which put them at increased risk for bleeding. Current literature suggests that using a single antiplatelet agent in combination with oral anticoagulation with a direct-acting oral anticoagulant (i.e., dual therapy) is effective and associated with less bleeding risk than triple therapy (dual antiplatelet therapy plus an oral anticoagulant) in patients with AF undergoing PCI with stent placement. The most recently studied dual therapy regimens consist of clopidogrel in combination with apixaban, rivaroxaban, or dabigatran. Guidelines recommend use of an oral anticoagulant plus clopidogrel and aspirin for a short period of time. In general, aspirin should be discontinued in most patients at discharge. In patients with a high risk of thrombosis, aspirin can be continued for up to 1 month. Dual therapy should be continued for 12 months, with oral anticoagulant monotherapy continued thereafter.

Conclusion

A review of current literature on antithrombotic therapy in patients with AF undergoing PCI and subsequent coronary artery stenting indicates that the favored regimen is dual therapy consisting of clopidogrel with rivaroxaban, apixaban, dabigatran, or a vitamin K antagonist. Aspirin may be used in the periprocedural period but should be discontinued thereafter to reduce the risk of bleeding. Decisions regarding specific agents and duration of treatment should be based on thrombotic risk, bleeding risk, and patient preference.
Genomic evidence of neo-sex chromosomes in the eastern yellow robin
Authors: Gan Han Ming , Falk Stephanie , Morales Hernán E , Austin Christopher M , Sunnucks Paul , Pavlova Alexandra
Published: September 2019

Background

Understanding sex-biased natural selection can be enhanced by access to well-annotated chromosomes including ones inherited in sex-specific fashion. The eastern yellow robin (EYR) is an endemic Australian songbird inferred to have experienced climate-driven sex-biased selection and is a prominent model for studying mitochondrial-nuclear interactions in the wild. However, the lack of an EYR reference genome containing both sex chromosomes (in birds, a female bearing Z and W chromosomes) limits efforts to understand the mechanisms of these processes. Here, we assemble the genome for a female EYR and use low-depth (10×) genome resequencing data from 19 individuals of known sex to identify chromosome fragments with sex-specific inheritance.

Findings

MaSuRCA hybrid assembly using Nanopore and Illumina reads generated a 1.22-Gb EYR genome in 20,702 scaffolds (94.2% BUSCO completeness). Scaffolds were tested for W-linked (female-only) inheritance using a k-mer approach, and for Z-linked inheritance using median read-depth test in male and female reads (read-depths must indicate haploid female and diploid male representation). This resulted in 2,372 W-linked scaffolds (total length: 97,872,282 bp, N50: 81,931 bp) and 586 Z-linked scaffolds (total length: 121,817,358 bp, N50: 551,641 bp). Anchoring of the sex-linked EYR scaffolds to the reference genome of a female zebra finch revealed 2 categories of sex-linked genomic regions. First, 653 W-linked scaffolds (25.7 Mb) were anchored to the W sex chromosome and 215 Z-linked scaffolds (74.4 Mb) to the Z. Second, 1,138 W-linked scaffolds (70.9 Mb) and 179 Z-linked scaffolds (51.0 Mb) were anchored to a large section (coordinates ~5 to ~60 Mb) of zebra finch chromosome 1A. The first ~5 Mb and last ~14 Mb of the reference chromosome 1A had only autosomally behaving EYR scaffolds mapping to them.

Conclusions

We report a female (W chromosome–containing) EYR genome and provide genomic evidence for a neo-sex (neo-W and neo-Z) chromosome system in the EYR, involving most of a large chromosome (1A) previously only reported to be autosomal in passerines.
Helping High School-Aged Military Dependents With Autism Gain Employment Through Project SEARCH + ASD Supports
Authors: Whittenburg Holly N , Schall Carol M , Wehman Paul , McDonough Jennifer , DuBois Thomas
Published: September 2019

Introduction: Youth with autism spectrum disorder (ASD) face high rates of unemployment, with unique challenges for military-dependent and -connected youth with ASD. This paper reports preliminary findings from Year One of a randomized waitlist controlled trial investigating the efficacy of the Project SEARCH + ASD Supports (PS + ASD) intervention model for military-dependent and -connected youth with ASD. Methods: Treatment group participants (n = 6) participated in internships at a military installation in the southeastern United States; waitlist group participants (n = 8) received special education transition services at their local high schools. Employment outcome data were collected at 12 months for both groups. Results: Fourteen unique internship experiences were developed across seven business partner organizations on the military installation during Year One. Five of six PS + ASD treatment group participants obtained competitive integrated employment for an overall employment rate of 83.3%. Four of the positions were federal jobs. None of the waitlist group participants obtained competitive integrated employment during the same period. Conclusions: Initial results are promising and suggest that the PS + ASD model may help to meet the transition needs of military-dependent and -connected youth with ASD and the employment needs of local military communities.