A practical framework for supplier selection decisions with an application to the automotive sector

One of the most strategic materials used in automotive industries is galvanised steel sheets, of which 50% to 85% of the weight of each car is made. However, these materials with the desired specification cannot be produced in Iran and must be outsourced to foreign providers. Therefore, outsourcing has become an indispensable part of Iranian automotive industries and a cooperative buyer-provider relationship is essential to survive and to acquire a reasonable profit. A recent approach in MCDM models is the BOCR analysis of Benefits, Opportunities, Costs, and Risks which evaluate both positive and negative aspects of each provider. However, due to the incommensurability among the composite priorities on the four merit factors, different synthesis approaches introduced in BOCR may offer different orderings of alternatives; which can be confusing for decision-makers to reach a final decision. On the other hand, the VIKOR method determines a compromise solution which is the closest to the ideal in the presence of conflicting and incommensurable criteria. This paper suggests integrated VIKOR-AHP-BOCR to select the best providers of galvanised steel sheets for IKCO that is the largest Iranian automaker. The proposed model and defined criteria can be used as a comprehensive guide by other companies for this purpose.     

Operating-curve selection for optical and digital correlation of fingerprints

We present a new method for selecting the optimal spatial light modulator operating curve on which to encode an ideal complex-valued filter function. The method is an extension of the optimization procedure that was used to derive the ideal complex-valued filter. To illustrate the method we consider the selection of a typical operating curve of a commercially available LCD and use this operating curve to encode a filter that was optimized for the task of fingerprint verification. We then extend the method to include the selection of the optimal operating curve from a series of synthetic operating curves.     

IQ不平衡OFDM系统两种逼近最大似然性能的亚最大似然补偿算法

针对在同相正交IQ不平衡的正交频分复用(OFDM)系统中用传统的最大似然(ML)补偿算法需要二维复向量的搜索,从而导致计算复杂度较高的问题,提出了两种逼近ML算法性能的补偿算法,即一维实向量迭代搜索算法和二维实向量迭代搜索算法,它们通过在空间中迭代搜索一维或二维实向量来降低计算复杂度.仿真结果表明,上述改进的亚ML补偿算法的性能优于现有的频域和时域最小二乘补偿方法,逼近ML算法,其计算复杂度明显低于传统的ML算法,误比特性能与ML算法相当.     

动目标/平台条件下的宽带相关处理

1引言宽带回波信号具有信息量大、混响背景相关性弱,有利于目标检测及其参量估计、特征提取等诸多优点。随着宽带信号在水声信号处理中的广泛应用,其回波信号处理的研究成为关键。本文在动目标/平     

Cross-layer adaptive resource allocation for OFDM systems with hybrid smart antennas

Orthogonal frequency division multiplex (OFDM) has become one of the most popular air-link technologies for future broadband wireless communications. To further improve its bandwidth efficiency and system performance, adaptive resource allocation and smart antenna techniques have been widely used in the OFDM system. However, the use of fully adaptive beamforming in an OFDM system significantly increases the complexity of the medium access control layer design and thus affects the implementation of adaptive resource allocation. A novel cross-layer adaptive resource allocation strategy with hybrid adaptive array and switched- beam smart antennas suitable for the OFDM systems has been proposed. With the help of different smart antennas schemes based on different users' quality of service requirements, the strategy effectively reduces the complexity of adaptive resource allocation in an OFDM system, while still maintaining a satisfactory system performance.     

A New Method for I/Q Impairment Detection and Evaluation in OFDM Transmitters

Detection and evaluation of impairments in the baseband section (I/Q impairments) of orthogonal frequency-division multiplexing digital transmitters are dealt with. A new measurement method is, in particular, proposed with the aim of overcoming key limitations exhibited by already-available approaches, which are generally designed for traditional digital transmitters and based on I/Q diagram analysis. The method is nonintrusive, exploits an analytical model that properly accounts for the way I/Q impairments affect the radio frequency output signal, with special regard to mirror subcarrier interference, and implements an original procedure to estimate impairment amounts. Aside from describing the analytical model along with the fundamental stages of the measurement procedure, this paper gives details of the extended experimental activity carried out on laboratory signals characterized by known I/Q impairments in order to assess the performance of the method.     

Broadband parallel-fiber optical link for short-distance interconnection with multimode fibers

In a multimode step-index fiber the propagation angle of a beam is conserved over short distances even if the fiber is bent slightly. This behavior can be exploited for a multiplexed signal transmission by the assignment of different channels to different propagation angles [angle-division multiplexing (ADM)]. Thus parallel transmission can be achieved. Because each channel occupies only a subrange of the fiber's numerical aperture, modal dispersion is reduced compared with single-channel transmission through the same fiber. The transmission properties of an ADM-based transmission line are analyzed for short propagation distances. Passive all-optical setups for multiplexing and demultiplexing operations are proposed. Cross-talk measurements are shown for a transmission with a length of 8 m and 13 multiplexed channels.     

Preamble design for joint estimation of CFO and I/Q imbalance for direct conversion OFDM system

This paper proposes a preamble structure for joint estimation of carrier frequency offset (CFO) and I/Q imbalance. Because existing methods cannot guarantee correct solutions within all range of CFOs, we derive two constraints of phase rotations applied to repetition patterns. By using the preamble based on the presented constraints, CFO is optimally estimated, and I/Q imbalance estimation is possible in all ranges of CFO with low complexity. Numerical results verify the importance and necessity of these constraints for joint estimation.     

下行多用户多业务OFDM系统动态资源分配方法

针对未来无线通信系统必须能够同时支持多种业务类型的用户的问题,按照各用户服务质量(QoS)需求的不同将用户分为具有不同优先级的类,并基于子载波与功率分配联合优化的思想,提出了一种下行多用户OFDM系统动态资源分配方法.仿真结果表明,与现有方法相比,该方法在首先满足具有较高优先级用户的QoS需求的情况下,将更多的资源分配给优先级相对较低的用户,从而提高了资源利用率,进一步增加了系统的整体速率.     

Complete validation for classification and class modeling procedures with selection of variables and/or with additional computed variables

The evaluation of the predictive ability of a model, is an essential moment of all the chemometrical techniques. So it must be performed very carefully. However, in the case of selection of relevant variables (an essential step in the case of data sets with many, frequently thousands, variables) the selection is generally performed using all the available objects. In some recent classification and class modeling techniques, from the original or from the selected variables the Mahalanobis distances of the leverages from the centroids of the categories in the problem are computed, and then added to the original variables. Also here the Mahalanobis distances are computed with all the objects. The consequence is an overestimate of the prediction ability, very large when the ratio between the number of the objects and that of the variables is rather low, so that the variance-covariance matrix is unstable.In this paper the correct validation procedures are described for the cases of selection of variables and of the addition of Mahalanobis distances computed on the original variables or the selected variables. The estimates of the prediction ability are compared with those obtained with insufficient validation strategies.     

Optimal training design for linearly time-varying MIMO/OFDM channels modelled by a complex exponential basis expansion

Time- and frequency-selective fading of propagating channels degrades the performance of multiple-input multiple-output/orthogonal frequency-division multiplexing (MIMO/OFDM) systems extensively by introducing double convolutions in both time-domain and frequency- domain. The author addresses the problem of linearly time-varying (LTV) channel estimation of MIMO/OFDM systems. First, the time-varying coefficients of the LTV channel are modelled by complex exponential basis expansions. Secondly, the LTV channel is estimated and the optimal pilot symbols are derived following the minimum mean square error criterion. It is shown that the optimal pilot strategy is to group consecutive pilot tones together as a pilot cluster and to distribute uniformly all pilot clusters in frequency-domain. In addition, the LTV channel estimation is further improved by imposing a window function on received signals. Finally, through simulations, it is shown that the new channel estimator can provide a considerable performance improvement in estimating MIMO-LTV channels, especially for the rapidly time-varying channel of a large Doppler frequency.     

Multiple comparisons with the best for supplier selection with linear profiles

In some manufacturing processes, the quality of a process or product is characterised by a linear profile. Comparing the process yield of multiple suppliers with linear profiles is an important task in supplier evaluation. In this study, we consider linear profiles with two-sided specifications and present the multiple comparisons with the best method based on the process yield index to select the best supplier. A subset contains the best supplier determined from the confidence interval of the difference between the process yield indices of the unknown best supplier and all of the suppliers. A simulation study is used to conduct the statistical power analysis. The results confirm that the larger the number of levels or the number of profiles, the larger the power of test. The simulation results indicate that our proposed method can effectively identify the best supplier. Two real examples are used to illustrate the applications of our proposed method.     

计量管理需要进一步与市场衔接

我国的计量法是基本适应当前的计量工作市场化水平的，但一些计量行政规范，与计量的市场化趋向和需要，有不适应的方面，与我国当前计量工作和国际规范接轨，有不适应的方面，因此必须改革，使我国计量工作走向法制化、国际化、市场化。     

Nonparametric tests for model selection with time series data

We consider a test for the selection of variables/covariates in a time series regression model based on aL ₂-measure of global deviation between the nonparametric estimates of the regression model obtained under the null and alternative hypotheses. Thus, the test can be viewed in the context of dimension reduction. Moreover, the test only requires, unlike others proposed for the same hypothesis testing problem, the choice of one bandwidth parameter. We show that our test has power against contiguous alternatives that converge to the null at a rateT ^−α, in contrast to alternative tests whose rates areT ^-α1, where 1/4 < α₁ < α 1/2. Thus the asymptotic relative efficiency of their test compared to ours is zero. Finally, the test is extended to the situation when the null follows a parametric model up to a finite set of parameters. This article is based on research funded by the Economic and Social Research Council (ESRC) reference number: R000235892.     

Integrated planning for product module selection and assembly line design/reconfiguration

To take full advantage of product modularity, modular product design and assembly system design/sreconfiguration have to be simultaneously addressed. The emerging reconfigurable production and flexible assembly techniques have made such an integrated approach possible. As such, this paper proposes an integrated approach to product module selection and assembly line design/reconfiguration problems. It further suggests that quality loss functions be used in a generic sense to quantify non-comparable and possibly conflicting performance criteria involved in the integrated problem. The complexity of the problem precludes the use of commercial software for solving meaningful sized problems in polynomial time. A genetic algorithm is therefore developed to provide quick solutions. An example problem is solved to illustrate the application of the proposed approach. Based on 72 randomly generated test problems, ANOVA analysis is further carried out to investigate the effects of genetic algorithm parameters. The convergence behaviour of the search processes is also examined by solving large problems with different numbers of operations and product modules.     

Necessary changes in the residential building sector to achieve the climate protection aims for 2030/2050

The aims of German energy and climate policy are ambitious: by 2050, emissions of greenhouse gases should be reduced by at least 80 %, ideally by 95 % compared to 1990. In addition, there are the decisions of the Paris Climate Accord, which intends to limit global warming to considerably less than 2°, better to 1.5°. The building sector as is known plays an important role in the energy transition. The transformation of the building industry and its thermal consumption is of decisive importance for the energy transition as a whole. A study recently commissioned by the alliance for building energy efficiency (geea), the German energy agency (dena) and further industry associations with the title ”Scenarios for a market‐based climate and resources policy 2050 in the building sector“ [1] shows clearly that the ”business as usual“ strategy will not suffice in order to even near the climate protection aims in the building sector. The scientific processing was undertaken by the ewi Energy Research & Scenarios, the institute for building services Dresden (ITG Dresden) and the research institute for thermal insulation (FIW Munich). The scope of this article only deals with the share of residential buildings.     

Integrating AHP with QFD for robot selection under requirement perspective

Selection of a robot is an important task, as improper selection may adversely affect a firm's production by reducing the quality of the product, thereby reducing productivity as well as profitability. To effectively select a robot for a specified job, several factors have to be considered. The objective of this paper is to explain how, using a combined AHP/QFD model, the authors are able to determine if the deployment of robots in industry helped in performance enhancement from requirement perspective. Incorporating a simple and novel cost factor measure in the proposed integrated AHP/QFD model aids justification of the implementation of a robotic system in a manufacturing firm from an economic point of view also. The proposed integrated approach also identifies technical requirements followed by customer requirements. In this paper, an integrated model combining AHP and QFD has been delineated for the industrial robot selection problem. Seven technical requirement factors have been considered for the case study.