Difficulties In Application Research Articles

Modern Methods for fast generation of digital holograms

With the advancement of computers, digital holography (DH) has become an area of interest that has gained much popularity. Research findings derived from this technology enables holograms representing three dimensional (3-D) scenes to be acquired with optical means, or generated with numerical computation. In both cases, the holograms are in the form of numerical data that can be recorded, transmitted, and processed with digital techniques. On top of that, the availability of high capacity digital storage and wide-band communication technologies also cast light on the emergence of real time video holographic systems, enabling animated 3-D contents to be encoded as holographic data, and distributed via existing medium. At present, development in DH has reached a reasonable degree of maturity, but at the same time the heavy computation involved also imposes difficulty in practical applications. In this paper, a summary on a number of successful accomplishments that have been made recently in overcoming this problem is presented. Subsequently, we shall propose an economical framework that is suitable for real time generation and transmission of holographic video signals over existing distribution media. The proposed framework includes an aspect of extending the depth range of the object scene, which is important for the display of large-scale objects.

THz-Imaging on its Way to Industrial Application

Terahertz radiation, which fills the gap between 100 GHz and 10 THz ( = 30 µm – 3 mm) in the electro-magnetic spectrum, has seldom been used outside of astronomy and other scientific research. However, in recent years there has been a significant interest in investigating THz radiation for different new applications. Especially the ability of terahertz radiation to penetrate deep into many organic materials without the damage associated with ionizing radiation such as X-rays lead to recent interests chiefly in the fields of security technology and biomedical imaging. The attribute of many different materials to be transparent for terahertz radiation, was also the reason for many difficulties in practical applications outside of research. Using radiation that can pass through so many materials so well makes detection difficult. In addition, sources to generate light at terahertz frequencies have suffered from low output intensity and other problems. Since the 1990s, technical breakthroughs in sources and detectors have brought terahertz technology within striking distance of significant commercial markets [1]. The pressure to develop new terahertz sources arose from two dramatically different groups - ultrafast timedomain spectroscopists who wanted to work with longer wavelengths, and long wavelength radio astronomers who wanted to work with shorter wavelengths. Today there are continuous-wave (CW) sources available as well as pulsed sources [2]. The aim of this paper is to provide an overview of key scientific developments which currently represent the basics of the mentioned THz technology. Beginning with the working principle of opto-electronic THz sources and detectors, the paper explains different setups for transmitting and using THz radiation. Furthermore it shows different applications of different business branches and gives an outlook for industrial application in the fields of metrology and quality control.

A new real-time algorithm for off-road terrain estimation using laser data

Gaussian mixture algorithm (GMA) is an effective approach for off-road terrain estimation, but still suffers from some difficulties in practical applications, such as complex calculation and object abstraction. In this paper, GMA ismodified to improve its real-time performance and to provide it with a potential ability of obstacle detection. First, a selection window is designed based on the dominant-ellipse-principle to limit the probability distribution area of each measurement point, therefore avoiding the calculation on the cells outside the dominant ellipse. Second, a clustering approach is proposed in order to distinguish objects efficiently and decrease the operation area of one laser scan. Third, a virtual point vector is introduced to further reduce the computational load of the mean square error matrix. The modified GMA is experimented on a tracked mobile robot, and its improved performance is shown in comparison to the original GMA.

Influence of the friction factor on the range of cement dispersion flow

Dispersial nature of cement grout makes many difficulties in practical applications of the injection process. It is also difficult to describe by theoretical equations. The rheological models treat cement paste as continuous material. In this paper the new flow equation was derived, which contains the factor of the friction between cement grains introduced to the Bingham model. The possibilities of the calculation of this new factor was presented. The analysis of the calculation’s results of the classical and new equations shows significant differences. The new equation allows to better predict the effects of the real injection applications.

Synthesis and characterization of polyethylene/C60 fullerene structures by photoluminescence

Fullerene C60 has attracted attention due to its special chemical and physical properties. However, its poor solubility and processability arise difficulties in practical applications. These problems may be surpassed by grafting C60 on polymers. This study presents the synthesis of the polyethylene/maleic anhydride copolymers and C60 structures and their characterization by photoluminescence. The synthesis of the material is based upon the reaction of fullerene C60 with amino groups containing in the polymer chains. In the first step, some polyethylene (PE)/maleic anhydride (MA) copolymers having 1, 3, 6 and 10 wt.% anhydride groups were reacted with an amine compound. The following step consists in the reaction of C60 with the amine groups. A proof that the structures synthesized contain C60 is given by the photoluminescence spectra.

Well-Balanced Scheme between Flux and Source Terms for Computation of Shallow-Water Equations over Irregular Bathymetry

Although many numerical techniques such as approximate Riemann solvers can be used to analyze subcritical and supercritical flows modeled by hyperbolic-type shallow-water equations, there are some difficulties in practical applications due to the numerical unbalance between source and flux terms. In this study, a revised surface gradient method is proposed that balances source and flux terms. The new numerical model employs the MUSCL-Hancock scheme and the HLLC approximate Riemann solver. Several verifications are conducted, including analyses of transcritical steady-state flows, unsteady dam break flows on a wet and dry bed, and flows over an irregular bathymetry. The model consistently returns accurate and reasonable results comparable to those obtained through analytical methods and laboratory experiments. The revised surface gradient method may be a simple but robust numerical scheme appropriate for solving hyperbolic-type shallow-water equations over an irregular bathymetry.

Integrating Multi-view Stereoscopic Transmission System into MPEG-21 DIA (Digital Item Adaptation)

In general multi-view system, all the view sequences acquired at the server are transmitted to the client. However, this kind of system requires high processing power of the server as well as the client, thus it is posing a difficulty in practical applications. To overcome this problem, a relatively simple method is to transmit only two view-sequences requested by the client in order to deliver a stereoscopic video. In this system, effective communication between the server and the client is one of important aspects. Therefore, we propose an efficient multi-view system that transmits two view-sequences according to user's request. The view selection process is integrated into MPEG-21 DIA (Digital Item Adaptation) so that our system is compatible to MPEG-21 multimedia framework. Furthermore, multi-view descriptors related to multi-view camera and systems are newly introduced. The syntax of the descriptions and their elements is represented in XML (extensible Markup Language) schema. Intermediate view reconstruction (IVR) is used to reduce such discomfort with excessive disparity. Furthermore, IVR is useful for smooth transition between two stereoscopic view sequences. Finally, through the implementation of testbed, we can show the valuables and possibilities of our system.

Partial distortion entropy maximization for online data clustering

Competitive learning neural networks are regarded as a powerful tool for online data clustering to represent a non-stationary probability distribution with a fixed number of weight vectors. One difficulty in practical applications of competitive learning neural networks to online data clustering is that most of them require heuristically-predetermined threshold parameters for balancing a trade-off between convergence accuracy, i.e. error minimization performance, and speed of adaptation to the changes in source statistics. Although adaptation acceleration is achievable by relocating a "useless" node so that it becomes useful, excessive relocation often disturbs error minimization. Hence, both of the adaptation speed and the error minimization performance sensitively depend on threshold parameters to determine whether a node should be relocated or not. In general, it is difficult to know adequate threshold parameters a priori. This paper proposes a novel criterion for decision making of node relocation without heuristically predetermined thresholds. According to the proposed criterion, a node is relocated only if the relocation task improves partial distortion entropy, which is an online optimality metric reliable from the viewpoint of error minimization. Hence, node relocation is carried out without disturbing error minimization. As a result, both quick adaptation and error minimization are simultaneously accomplished without any carefully predefined parameters. Experimental results clarify the validity of the proposed criterion. Competitive learning with the criterion is clearly superior to other representative algorithms in terms of both quick adaptation and error minimization performance.

데이터베이스 기반 유전 알고리즘을 이용한 효율적인 에어포일 형상 최적화에 대한 연구

Genetic Algorithms(GA) have some difficulties in practical applications because of too many function evaluations. To overcome these limitations, an approximated modeling method such as Response Surface Modeling(RSM) is coupled to GAs. Original RSM method predicts linear or convex problems well but it is not good for highly nonlinear problems cause of the average effect of the least square method(LSM). So the locally approximated methods, so called as moving least squares method(MLSM) have been used to reduce the error of LSM. In this study, the efficient evolutionary GAs tightly coupled with RSM with MLSM are constructed and then a 2-dimensional inviscid airfoil shape optimization is performed to show its efficiency.

Experimental Analysis of 3D Flow in Scroll Casing of Multi-Blade Fan for Air-Conditioner

The multi-blade fan, which has been widely used as a blower for air-conditioning systems of vehicles, is one of the well-established fluid machinery. However, many factors must be considered in its practical design because the flow generated in the fan is quite complicated with three-dimensionality and unsteadiness. The fundamental fan performance is primarily determined by the impeller of the fan, and is also affected by the scroll casing. However, the theoretical estimation of the effect of the casing on the performance has not been well established. In order to estimate the casing effect on fan performance, detailed three-dimensional (3D) flow analysis in the casing is necessary. Stereoscopic PIV (SPIV) is one of the useful techniques for experimental analysis of 3D flow fields. There are some difficulties in practical application of SPIV for flow analysis in fluid machinery with complicated geometry, but the results obtained provide useful information for understanding the 3D flow field. In this report, experimental investigation of the flow in the scroll casing has been carried out using PIV and SPIV under the premise of downsizing automobile air conditioner fans.

Robust Parameter Design via Taguchi’s Approach and Neural Network

The parameter design is the most emphasized measure by researchers for a new products development. It is critical for makers to achieve simultaneously in both the time‐to‐market production and the quality enhancement. However, there are difficulties in practical application, such as (1) complexity and nonlinear relationships co‐existed among the system’s inputs, outputs and control parameters, (2) interactions occurred among parameters, (3) where the adjustment factors of Taguchi’s two‐phase optimization procedure cannot be sure to exist in practice, and (4) for some reasons, the data became lost or were never available. For these incomplete data, the Taguchi methods cannot treat them well. Neural networks have a learning capability of fault tolerance and model free characteristics. These characteristics support the neural networks as a competitive tool in processing multivariable input‐output implementation. The successful fields include diagnostics, robotics, scheduling, decision‐making, prediction, etc. This research is a case study of spherical annealing model. In the beginning, an original model is used to pre‐fix a model of parameter design. Then neural networks are introduced to achieve another model. Study results showed both of them could perform the highest spherical level of quality.

Defect imaging with guided waves in a pipe

Guided wave techniques are expected to become an effective means for rapid, long-range inspection of pipes. Such techniques still have many practical difficulties in application, however, due to the complex characteristics of guided waves such as dispersion and their multimodal nature. A defect imaging technique is developed in this study to overcome the complexities of guided wave inspection. Received signals are separated into single-mode waveforms with a mode extraction technique and then spatial waveforms on the pipe surface at an arbitrary time are reconstructed. The predicted waveforms can provide a defect image at the moment when an incident wave arrives at a defect region, which is based on a time-reversal technique. This defect imaging technique is experimentally verified using eight signals detected at eight different circumferential positions. Images of artificial defects are obtained with one-hole and two-hole test pipes, and increasing the frequency of incident waves increases the resolution of the images. Holes and pipe ends are recognizable in the images, but the reconstructed images contain some errors in the area behind the defects where guided waves do not propagate or do not reflect back to the receiving transducers.

Subwavelength imaging by a left-handed material superlens.

In this work, a finite-difference time-domain (FDTD) method is employed to justify the superlensing effect of left-handed material (LHM) slabs. Our results demonstrate that subwavelength resolution can be achieved by LHM slabs with certain parameters. We present the dynamic feature of the imaging process and the dependence of physical parameters on the performance of the superlens. These results help to clarify the diverse FDTD results reported previously. We also show that the achievable resolution is limited by the absorption and thickness of the LHM slabs, which introduces difficulties in practical applications of the superlens.

The meaning of mental illness within the Victorian Mental Health Act: the problem of definition

This study will critically examine the Mental Health Act 1986 (Vic), including the significant changes introduced through the Mental Health (Amendments) Act 1995 (Vic). It will be argued that the Victorian legislation presents some practical difficulties in application as it adopts too broad a definition of mental illness to be used reliably in assessing a person's need for treatment and/or criminal responsibility within a court of law. This lack of precision is potentially problematic for social workers and lawyers alike with respect to key decisions regarding assessment for mental health services and assigning criminal responsibility before the law. Implications for social work practice will be briefly discussed.

Socioeconomic cost-effectiveness analysis--occupational rehabilitation between effectiveness and social compatibility

The fundamental question in case of planning projects of the state is which pros and cons are involved in their realization. Public projects take up a lot of social resources which hence are no longer available for other purposes--especially when you look at existing budgetary limits. A decision in favour of one specific project always implies a decision against some other project. A classical method to evaluate public projects is the cost-benefit analysis, which leads a shadowy existence owing to its difficulties in practical application (first and foremost in identifying and quantifying). In this article a possible application for cost-benefit analysis is demonstrated on the example of an institution for initial vocational training of young people with disabilities or at risk of becoming disabled. The main point here is to widen the focus from simply looking at fiscal expenses, revenues and savings towards also taking notice of social, psychological and health orientated facts. In this view it is very consequent to enlarge the "normal" economic balance sheet by drawing up a special social balance sheet which illustrates advantages and disadvantages difficult to measure at a monetary basis. A comprehensive decision basis is thereby achieved considering "both sides of the medal".

Computation of molecular integrals over Slater-type orbitals. VII. Calculation of multielectron molecular integrals by single-center expansion method using different translation formulas

Hitherto known formulas for the translation of Slater-type orbitals (STOs) from one center to another encounter serious difficulties in practical applications. In contrast, those derived by the use of arbitrary complete orthonormal sets of exponential-type functions (ETFs) expansion formulas appear to be free of these difficulties. We have examined in this paper the applicability of translation formulas for STOs obtained from the two kinds of ETFs, namely, from the Lambda ( Λ) and Coulomb Sturmian (CS) functions (Int. J. Quant. Chem. 81 (2001) 126) to the quantum-mechanical multicenter problems from the computational point of view and found it very useful. Test calculations on three-center nuclear attraction and four-center electron-repulsion integrals by single-center expansion method are reported. It is shown that these integrals in the case of Coulomb Sturmian ETFs exhibit a faster convergence rate. Therefore, it is recommended to use the expansion formulas for translation of STOs, obtained from the Coulomb Sturmian ETFs, in the calculation of multielectron multicenter molecular integrals.

A remedy for the temperature recovering method of solidification simulation

One of the methods of phase change simulation is the “temperature recovering method.” It has two main difficulties in practical application. The first one is the explicit nature of the method. The second one is the slow convergence of the solidification ratio. In this study, a method has been proposed to improve these difficulties. The method consists of two procedures. First, the solidification range is clustered into a discrete variable. A solidification ratio is sorted within a cluster as an integer variable. Second, the source term related to the change of the latent heat is reformulated into an implicit form by the “numerical linearization method” as previously proposed by the author. The benchmark test cases show that: (1) The convergence is faster, even for large latent heat cases, than the existing method. (2) The stability is independent of the time increment. © 2000 Scripta Technica, Heat Trans Asian Res, 29(5): 400–411, 2000

Beyond Jones v. Clinton: sexual harassment law and social work.

In the wake of the Jones v. Clinton case, there has been a renewed interest in sexual harassment issues, particularly the chaotic case law in this important field of practice. The author urges the social work profession to resurrect its commitment to achieving social justice by participating in the current efforts to unravel the complexities of sexual harassment law. Toward this end, the article presents an analysis of the concept of sexual harassment by providing an overview of the legal issues and case law to highlight the statutory questions that have left the judicial system confounded by the difficulties of practical application of the law. Furthermore, the article deals with the relevance of this topic for the professional mission and suggests the utility of some conceptual frameworks and key concepts that might help social workers to address the clinical, administrative, and advocacy concerns in this substantive area.

A remedy for the temperature recovering method of solidification simulation

One of the methods of phase change simulation is the temperature recovering method. It has two main difficulties in practical application. The first one is the explicit nature of the method. The second one is the slow convergence of the solidification ratio. In this study, a method has been proposed to improve these difficulties. The method consists of two procedures. First, the solidification range is clustered into a discrete variable. A solidification ratio is sorted within a cluster as an integer variable. Second, the source term related to the change of the latent heat is reformulated into an implicit form by the numerical linearization method as previously proposed by the author. The benchmark test cases show that: (1) The convergence is faster, even for large latent heat cases, than the existing method. (2) The stability is independent of the time increment

Improved feature selection and classification by the 2-additive fuzzy measure

This paper focusses on the investigation of a pattern recognition method based on the fuzzy integral. Until now this method has used a general fuzzy measure, which is characterized by exponential complexity. Naturally this led to some difficulties in practical applications of this pattern recognition method. In this paper, a heuristic algorithm for the identification of the 2-additive fuzzy measure, which is a particular type of k-additive fuzzy measures, is proposed. This algorithm can be used to reduce complexity of feature selection and classifier design. A further topic considered in this paper is the development of a feature selection algorithm for the fuzzy integral classifier. The proposed heuristic algorithm is based on two feature-evaluation criteria such as the importance and the interaction indexes. They were earlier defined in the literature using the semantic interpretation of the fuzzy measure. To validate the proposed algorithms, the feature selection algorithm and the pattern recognition method based on the fuzzy integral are applied to a problem of acoustic quality control.