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分散式快取在Rails上的應用;The Application of Distributed Cache with Rails
No full text[[abstract]]隨著網路蓬勃發展以及網路使用者的急速成長已經對網路的負荷相對成長。為了解決網路流量與頻寬的問題，網路設備中的快取伺服器(Cache Server)可以有效減輕網路的負擔，達到降低頻寬的需求。[1]現今的網路平台大部分都是在中央式的伺服器上架設，我們希望以去中心化的方式開發網路平台。此分散式平台為一個擁有各式各樣的服務並提供獨立自主的分散式平台，每位使用者的資料都可以存在自己的節點裡，此平台叫做WeOS，該平台提供匯集真相的公開討論版(OurTruths)、聊天室(OurChat)、拍賣網站(WeSale)...等服務。由於分散式環境的關係，若是使用者想同步在各個不同節點的資料，就必須要有個同步機制，而資料的同步將會衍生出資料一致性(cache coherence)的問題。本論文將針對此問題來開發出一套基於快取伺服器(Cache Server)概念的應用，以提供WeOS平台暫存資料與同步機制，並解決同步機制所衍生出的資料一致性問題
利用適應值繼承增強演化演算法;Boosting Evolutionary Algorithm through Fitness Inheritance
No full text[[abstract]]適應值估計已被廣為應用於現實問題，目前的適應值估計方法可被分為兩類；適應值繼承與代理模型。代理模型利用低計算資源的模型取代適應值函數；而適應值繼承基於親代之適應值估計子代之適應值。在模型的準確度與複雜度間存在折衷，由於不具有建模程序適應值繼承較代理模型有更低的計算資源消耗，相對地代理模型則有較適應值繼承更高的準確度。本研究利用適應值繼承解決設計適應值估計方法的關鍵議題，包含冷啟動、模型管理、模型選擇、演化控制、以及準確度與複雜度的折衷。具體而言，本篇研究提出三個架構，即適應值繼承輔助代理模型、基於主動式學習之適應值繼承、以及基於適應值估計的共生群落演化。首先，適應值繼承輔助代理模型提出先期建模、適應值繼承與代理模型之結合、以及基於適應值繼承之模型管理標準分別解決冷啟動、模型選擇、模型管理三個議題。實驗研究驗證適應值繼承輔助代理模型與一先進方法—代理輔助瀰因演算法—較之皆具有效度與效率。然而，適應值繼承輔助代理模型仍考慮代理模型的使用造成效率上的瓶頸。為解決此一議題，基於主動式學習之適應值繼承利用適應值繼承的集成結合基於不同距離評估之適應值繼承建立一具效度與效率之估計模型。基於主動式學習之適應值繼承並引入主動式學習的概念擴展演化控制的觀點。實驗研究驗證基於主動式學習之適應值繼承架構較代理輔助瀰因演算法以及適應值繼承輔助代理模型架構更具效度與效率。在單工最佳化之上，將適應值估計方法用於演化式多工進而產生基於適應值估計的共生群落演化。啟發自生物群落中之共生關係，基於適應值估計的共生群落同時演化多個群體作為生物群落，並以群體間的訊息交換模擬共生關係。候選解的選擇是自一連結後代經由不同工作上建立之估計模型所成之集成做為評估標準選出。此外，本研究提出一組演化多工的測試問題以驗證效能。實驗結果證明基於適應值估計的共生群落演化較先進的單工演算法—共變矩陣適應演化策略、一知名演化多工演算法—多因子演化演算法、以及基於主動式學習之適應值繼承架構，皆能有更好的效度與效率。實驗並證明基於適應值估計的共生群落演化更優於一演化多工的先進算法。
Fitness approximation methods have been widely used to solve complex benchmark problems and real-world applications. Current approaches of fitness approximation can be categorized into two types: fitness inheritance and surrogates. Surrogate model adopts a computationally less expensive model for fitness function, while fitness inheritance approximates the fitness on the basis of parent’s fitness. There is a trade-off between model complexity and model fidelity. Though fitness inheritance is computationally cheaper than surrogates due to the lack of modeling process, surrogates can have higher fidelity than fitness inheritance. This study utilizes fitness inheritance to address the key issues in the design of fitness approximation, i.e., cold start, model management, model selection, evolution control and fidelity-complexity trade-off. Specifically, three frameworks are proposed in the present study, i.e., fitness inheritance aided surrogates (FIS) framework, active learning based fitness inheritance (ALFI), and evolution of biocoenosis through symbiosis with fitness approximation (EBSFA). First, the FIS framework presents early modeling, collaboration of fitness inheritance and surrogates, and inheritance-based model management criterion to tackle the cold start, model selection, and model management issues, respectively. Empirical studies verify that FIS framework is effective and efficient in comparison to a state-of-the-art surrogate-assisted memetic algorithm (SAMA) on CEC 2014 test problems. Nonetheless, FIS framework still considers the use of surrogates which becomes a bottleneck of efficiency. To address this issue, the proposed ALFI ponders fitness inheritance with ensemble which integrates fitness inheritance with different distance measures for generating an effective and efficient approximation model. Introducing the concept of active learning in the ALFI broadens the view of evolution control. Empirical results validate that ALFI framework has effectiveness and efficiency, in comparison to SAMA and FIS framework. Beyond single task optimization, extending the use of fitness approximation on evolutionary multitasking leads to the EBSFA. Inspiring from symbiosis in biocoenosis, the EBSFA evolves several EAs concurrently as biocoenosis and exchanges information among EAs as symbiosis. The selection of candidate individuals to be evaluated among a concatenate offspring is taken by the ensemble of multiple fitness approximation derived from different tasks. In addition, this study proposes a set of new benchmark problems for evolutionary many-tasking (MaTPs) to validate the performance. Experimental results exhibit the effectiveness of the proposed EBSFA framework over a state-of-the-art numerical optimization method, the covariance matrix adaptation evolution strategy (CMAES), a well-known evolutionary multitasking method, the multi-factorial evolutionary algorithm (MFEA), and the ALFI framework on the four MaTPs. The EBSFA also outperforms a state-of-the-art evolutionary multitasking method on the benchmark problems of CEC 2017 competition for multitask optimization
定位移動設備透過兩節點以及鄰居檢測的方法;To Localize Mobile Devices via the Two Nodes and Neighbors Examining Technique
No full text[[abstract]]在一些特殊環境中，並非每一個移動設備都配置GPS或者知道自己本身的位置(像是森林、室內…等等)，只有少部分移動設備能夠知道自己位置，所以往往無法有足夠的錨節點去做三角定位來估算出目標節點的位置。利用兩個節點以及一個鄰居檢測的方法來提高在無線感測網路中的節點定位能力是很有效的。特別是在節點分佈稀疏或者錨節點數量稀少的情況下更是明顯的有用。只需要兩個位置以知的節點再加上一個鄰居檢測，即使沒有三個位置以知的鄰居在周遭利用三角定位演算法來做定位，還是可以成功定位出目標節點的位置。為了模擬移動設備的移動性，這篇論文中模擬了不同的移動模型。移動模型代表著節點的移動模式，它的移動速度、方向會隨著時間流逝而變化。不同的移動模型都有不同的特性以及限制，使得節點的移動特性有所不同，定位演算法的效能有會因此而受到影響。 在本論文中，我們移動性對於利用兩個節點以及一個鄰居檢測的方法所帶來的影響感到興趣。也因此我們利用移動模型模擬了移動設備的移動性，並且利逾兩個節點以及一個鄰居檢測的方法來定位移動設備。我們在本論文中還比較了不同種類的移動模型所帶來的影響，像是隨機遊走、隨機方向、隨機目的地。並且針對移動性所帶來的影響我們也提出了一個改善的方法來提高定位的穩定度。 我們利用移動設備上次被定位的位置來當作錨節點，藉此協助做定位。經過實驗結果證明，該方法可以顯著的提高定位率，特別是在節點數量稀少的情況下，並且可以提高定位率的穩定度，然而距離誤差會隨著節點成功定位的數量些許增加。
Using two nodes and neighbors examining to improve positioning capability in wireless sensor networks (WSNs) is useful. Particularly in sparse sensor network, the nodes can be located without three position-known neighbors as long as it has two position-known nodes and one neighbor. Contrast to static WSN, more challenges and opportunities occurred in mobile wireless networks (MWSNs).To simulate the mobility of the WSN, different kinds of mobility model is used. Mobility model represents the movement of the nodes, and how their speed, location, and direction change overtime. Each model has its own characteristics, working capacity and limitations. In this paper, we are interested in studying the impact of mobility of the WSNs. We simulate the positioning approach “Using two nodes and neighbors examining” in MWSNs. We also present the comparative of using this approach in different kinds of mobility models, such as Random Walk, Random Waypoint, Random Walk Model and Random Gauss-Markov Model. At last, we proposed a method to enhance the stability of the WSN structure. We using the nodes last located position as an anchor nodes. The experiment result shows this method can significantly improve the position rate, especially when the nodes sparse distributed. However the distance measurement errors will increase
可應用於人體通道傳輸且具有快速相位追蹤功能的無參考時脈全數位資料與回復電路設計;A Fast Phase Tracking Reference-Less All-Digital CDR Circuit for Human Body Channel Communication
No full text[[abstract]]隨著科技進步，穿戴式的裝置與個人醫療照護的裝置蓬勃發展。在傳統上，許多醫療的設備，如心電圖、肌電圖皆使用電線來傳遞訊號，對病人來說造成許多不方便，因此無線的人體區域網路開始發展，目前的無線人體區域網路技術透過空氣來傳遞訊號如藍芽、ZigBee，然而都有功率過高以及傳輸速率慢的缺點，因此人體通道傳輸的技術被用於解決這些問題，人體通道傳輸使用人體當成傳輸媒介。人體通道傳輸具有較低的訊號衰減且不容易遭受周遭環境的干擾，此外，人體通道傳輸能達到較高的傳輸速率。 本論文介紹一個寬帶訊號傳收器。在傳送端，資料會使用 NRZI 編碼與位元填充增加資料的變化，且使用封包式傳輸。在接收端，我們採用無參考時脈的資料與回復電路設計，因此可以降低功率的消耗以及減少電路的複雜度，且我們利用多相位來量化相位誤差的方法能夠增加資料與回復電路追蹤能力以及快速的補償相位誤差。此外，在不同的製程、溫度、電壓的變異下，我們所提出的自動校正相位追蹤量方法，能夠計算出補償碼並提供給全數位資料與回復電路控制器，保證在不同的環境變異下，動態地進行控制碼調整增益的補償。
As technology advances, the wearable personal entertainments and personal healthcare devices are booming. Traditionally, the medical healthcare devices such as electromyography (EMG) and electrocardiography (ECG) use the wireline to transfer the physiological signals, it leads to inconvenient for patients. Therefore, the wireless communication techniques are used to solve this problem. The common type of wireless body area network (WBAN) realization transmits data through the air, such as Bluetooth and ZigBee. However, they have relatively high power consumption and relatively low data rate. Therefore, the body channel communication (BCC) is proposed to solve this problem. The wireless communication transmits the data through the air, but the BCC uses the human body as the communication channel to transmit the data. Moreover, the BCC has relatively low signal attenuation and relatively few interferences in the nearby environment. Furthermore, the BCC can achieve a high data rate. In this thesis, a wideband signaling (WBS) transceiver is proposed. In transmitter part, the data are modulated by a non-return to zero inverted (NRZI) encoder with a bit stuffer. The data are transmitted in the packet format. In the receiver part, the proposed reference-less clock and data recovery circuit (CDR) can reduce the power consumption and circuit complexity. Moreover, the proposed phase error calculation method uses the multi-phase signals to quantize the phase error. The proposed method can enhance the CDR phase tracking ability and compensate for phase error quickly. The proposed automatically phase track gain calibration method can calculate the gain value for the all-digital CDR (ADCDR) controller. In different process, voltage and temperature (PVT) variations, the gain value will be automatically calibrated
結合Kinect的籃球運球自主訓練輔助系統;Kinect-Based Autonomous Training Assistant for Basketball Dribbling
No full text[[abstract]]籃球運球的訓練對於初學者來說必須要由教練教導每一個動作的細節、重點並從旁即時糾正錯誤，才能正確、有效的學習；有一定基礎後可以看影片跟著做訓練，但是動作的正確性無法客觀的確認。因此我們提出一套結合Kinect的輔助系統，讓使用者進行籃球運球的自主訓練時能有更大時間彈性，並在訓練中提供即時回饋以及訓練結束時的評分，以確保訓練的成效。 使用Kinect以及其骨架追蹤技術可以得到使用者的骨架資訊。而改良現有物件偵測與追蹤方法後我們可以由Kinect取得的影像中即時且自動地偵測與追蹤籃球。另外在姿勢辨識部分，利用Microsoft提供的工具Visual Gesture Builder（簡稱VGB）能將分解後動作細項自定義為各個獨立的姿勢並以機器學習的方法建立姿勢資料庫。我們結合骨架資訊、球的位置以及姿勢辨識來完成自主訓練輔助系統。 相較於以往請教練或自己看影片跟著做，我們的系統一樣能讓使用者知道哪部分需要改進，輔助使用者進行籃球運球自主訓練，解決需要教練陪同或沒有客觀檢查動作的問題。特別強調我們不是要取代傳統教練的角色，而是讓球員和教練都有更大的時間彈性，像是延伸應用到球隊上，教練可以決定訓練菜單的動作和分數的標準等等，訓練結束後收到球員們的訓練報告。讓球員能在一段時限內自己選擇時間完成訓練，也讓教練能一次教導更多的球員。
For beginners, basketball dribbling training requires instructions from coaches. To ensure the training is effective, coaches usually teach details and emphases of each move and correct mistakes right away as a bystander. Then, they might just need training videos to practice autonomously, but the correctness of moves is not able to confirm objectively. Therefore, we present a Kinect-based assistance system for user to train autonomously at home or community centers no matter when. Moreover, our system is able to provide visual feedback of each move in real-time to ensure the correctness. We can get user’s skeleton information by using Kinect and Kinect skeletal tracking algorithm. We can also automatically detect basketball and get its location in real-time by improving existing object detect and tracking algorithm with color, depth, and body index images obtained from Kinect. For posture recognition, we separated dribble moves into details and emphases, defined these as independent postures, and built posture database by using a machine learning based tool－Microsoft Visual Gesture Builder. By combining skeleton, ball locations, and posture recognition, we can achieve our goal. Our system solves problems such as no coach as bystander or no objective confirmation of correctness of moves. Note that our system does not aim to replace conventional role of coaches, but to allow players and coaches to have more time flexibility. In addition, our system can be applied to serve a basketball team. Coach decides training menu, emphases of moves, and passing standard for each player and gets reports after players finish their training. Therefore, coach can teach more players at once, and player can choose when he/she wants to train in a time limit
基於樂理之演化式自動作曲;Automatic Music Composition Using Evolutionary Algorithm Based on Music Theory
No full text[[abstract]]With the development of science and technology, applications of computer are more and morecomprehensive. Using artificial intelligence (AI) to drawing, thinking, and problem solving becomesa significant topic. Recently, research on automatic composition using AI technology andespecially evolutionary algorithms is blooming and has received promising results. However, mostof the automatic composing systems based on evolutionary computation require human feedbackas evaluation criterion, which is vulnerable to the fatigue and decreased sensitivity after long-timelistening. This research proposes using music theory in the evaluation criterion to substitute thefeedback from human. Specifically, we generate the weighted rules based on music theory for thefitness function. We also develop strategies for determining the weights according to human expertand the music download charts. In addition, this study proposes an automatic accompanimentevolutionary system to coordinate with the main melody. The musical form is applied to integratethe structure of music compositions. This study additionally proposes a special fitness functionfor Chinese music, which combines both the Western and Chinese music theories as the basis toevolve. Additionally, we present a fusion system which considers the musical rules from Flamencoand Argentine Tango to achieve the synthesis of differentmusical genres. The resultingmusic showsthat the proposed methods can effectively achieve satisfactory compositions. Besides, we proposeusing the k-th nearest neighbor (KNN) to predict the popularity of music. In this study, we adopt47 rules frommusic theory as features and analyze a specific musician’s 101 compositions to calculatethe frequency of the adopted rules. The trained KNN model is further used for the evaluationcriteria of composing
海外投資對多國籍企業績效關聯之實證研究-區域不動產價值之影響;The Relationship between overseas investments of multinational enterprises and performance-Impact of regional real estate values
No full text[[abstract]]過去文獻曾提出資本流入鴻運現象(capital inflows bonanzas)，並認為地區不動產價格會在大規模的資本流入後呈現上漲的趨勢。本研究則透過分析台灣之多國籍企業，發現當公司海外投資規模越高時績效表現反而較差，推論可能原因為管控距?較遠、文化及語言隔閡、技術上的差?與消費者偏好等因素，?會增加額外成本。尤其是電腦及設備周邊產業進行海外設廠時，通常需購置廠房土地、添購大規模的機器設備以供生產，其資金龐大，導致多國籍企業平均的績效反而愈差。最後在區域不動產價值構面部分，研究結果則顯示全球加權房產價格的確會影響多國籍企業績效，代表多國籍企業於房產價格越低時購置廠房，對多國籍企業績效越有利。
Prior studies once documented the phenomenon of the capital inflows bonanzas. Namely, real estate prices will go up after a large scale capital inflow. Employing multi-national enterprises in Taiwan, this study finds that companies with higher overseas investment have lower financial performance. This may arises from far distance, cultural and language barriers, differences in technology and consumer preferences, etc. In particular, the demand for large fund to purchase property, equipment, and set up factories overseas in the computers and the associated peripherals industry contributes to the underperformance of these multi-national enterprises. From the real estate price perspective, results show that global weighted real estate prices do affect the performance of multi-national enterprises, implying that performance will be higher when multi-national enterprises purchase real estate at a lower price
教育體系之內部控制與稽核之研究—以私立學校人事事項為例;Research on Internal Control and Auditing of Education System — A Case Study of Private School Personnel Matters
No full text[[abstract]]教育事業向來被視為百年大業，而辦校興學，更被譽為是春風化雨、作育英才的公益行為。然而數十年來私立學校弊案叢生，讓教育界蒙上層層的陰影；私立學校董事會發生的舞弊案件包括：董事會糾紛、掏空財務、不法買賣席次、以少報多購置校產、帳務登載不實等。教育是非營利組織中最大的組織之一(Levey, 1986)，而學校是正規教育最重要的核心，私立學校在我國的教育體制中佔有重要的地位(林本炫，2006)。因此本研究將依據私立學校內部控制制度來探討並研究下列各問題：一、目前台灣私校教育體系可能面臨之問題及其發生原因。二、台灣私校教育體系之內部控制制度在私校人事事項方面之重要性。三、私校教育體系之內部控制在人事事項方面可行之內部稽核項目。四、私校教育體系之內部控制在人事事項方面之評估機制。 透過文獻探討、個案研究法及專家問卷調查後，本研究得以下之結論：一、目前台灣私校教育體系在內部控制方面所面臨的問題相當多，其重點歸納有：招生問題、校園問題、教師學術研究費問題，以及教職員工年終獎金發放問題等。二、私校教育體系之內部控制制度在人事事項方面，不管是在學校立場或是在教師立場，都具有相當重要性，是一個保障學校與教師雙方之權利與義務之制度。三、本研究依據「學校財團法人及所設立學校內部控制制度」在人事事項方面之控制重點及「高級中等學校校務評鑑」在人事行政管理方面之參酌指標，擬定了可行性之內部稽核計畫表(內部稽核項目)。四、私校教育體系在內部控制方面之評估機制可分為「整體層級」及「作業層級」。而評估項目，是以學校各單位對於風險評估後之「高風險值」項目作為內部控制自行評估之控制作業項目。
Education has always been regarded as a hundred years of the great business, and estabished a school to construct teaching living space, but also known as the spring rain, the education of the public welfare behavior. However, decades of private school fraud, so that the education sector cast a shadow; private school board of directors of the fraud cases include: the board of directors disputes, hollowed out the financial, illegal trading seats, to less reported more purchase school, Not real and so on. Education is one of the largest organizations in nonprofit organizations (Levey, 1986), and schools are the most important core of formal education. Private schools play an important role in our educational system (Lin Ben Hyun, 2006). Therefore, this study will be based on the private school internal control system to explore and study the following issues:First, the current Taiwan private school education system may face the problem and its causes.Second, the Taiwan private school education system of internal control system in the private school personnel matters of importance.Third, the private school education system of internal control in personnel matters feasible internal audit project.Fourth, the private school education system of internal control in the personnel matters of the assessment mechanism. Through the literature, case study and expert questionnaire survey, this study has the following conclusions:First, the current private education system in Taiwan in the internal control of the problems faced by a considerable number of its focus are summarized: enrollment, campus problems, teachers, academic research fees, and staff year-end bonus issue.Second, the private school education system of internal control system in personnel matters, whether in school position or in the teacher's position, are of great importance, is a guarantee of both schools and teachers of the rights and obligations of the system.Third, the study based on the "school company and the establishment of the school internal control system" in the personnel matters in the control of the focus and "senior secondary school school assessment" in the personnel administration of the reference indicators, the feasibility of the internal audit Plan (internal audit project).Fourth, the private school education system in the internal control of the assessment mechanism can be divided into "the overall level" and "operational level." The evaluation project is based on the self-evaluation of the "high risk value" project after the risk assessment of the school units as the internal control
法人說明會影音資訊與資金成本之關聯性;The Association between Video Conference Call and the Cost of Capital
No full text[[abstract]]近年來，越來越多上市櫃公司藉由召開法說會揭露增額資訊，並作為與市場參與者重要的溝通平台。我國主管機關金管會修訂法規，自2013年6月起上市櫃公司於國內自辦法?會須上傳影音檔案至網路，使得法說會資訊更為公開且即時，亦為債權人評估授信之參考依據。本研究以2013年6月至2015年年底上市公司自辦法說會影音資訊為研究對象，探討其法說會特徵（法說會的時間長度、用詞、公司參與人數及問題數），是否會對負債資金成本造成影響。實證結果發現法說會用詞越樂觀，負債資金成本越高。
Recently, more and more listed companies hold conference calls to disclose additional information and create a sighnificant communicate platform with market participants. Taiwan Financial Supervisory Commission（FSC） revise the law to mandatory require the listed companies holing conference calls to upload their video conference call on the internet. Therefore, the information of conference call becomes more instantaneous and transparent; as well as providing references for the credit assessments. In this study, we make the voluntary vedio conference call of listed companies from June 2013 to the end of 2015 be the subjects. The purpose of this study is to explore whether the features of conference call affect cost of debt capital. We find that companies with the more positive tone in the conference call are associated with higher costs of debt capital
成本僵固性與分析師盈餘預測之關聯性;The Relationship Between Cost Stickiness and Analyst Earnings Forecast.
No full text[[abstract]]本研究主要探討成本僵固性對分析師盈餘預測之影響，本文將從三個角度切入探討，首先探討成本僵固性是否會影響分析師盈餘預測。第二，成本僵固性是否會影響分析師追蹤人數。第三、將銷售預測納入考量，探討分析師是否了解企業成本僵固性，並額外探討投資人之盈餘驚喜反應是否受成本僵固性影響。本研究以國內非金融業之上市櫃公司以及券商分析師之預測為研究對象，研究期間為2014第4季至2016第4季，利用敘述性統計、相關係分析及多元回歸進行實證分析。實證結果顯示，成本僵固性不會影響分析師盈餘預測、分析師追蹤人數及投資者對盈餘驚喜之反應；若將銷售預測納入考量，實際銷售額大於分析師銷售預測時(即favorable) 成本愈僵固之公司，每單位銷售預測錯誤與盈餘預測錯誤之比例愈小，費用預測錯誤愈大；實際銷售額小於分析師銷售預測時(即unfavorable)成本愈僵固之公司，每單位銷售預測錯誤與盈餘預測錯誤之比例愈大，費用預測錯誤愈小，且當銷售未達預期時，成本僵固性影對每單位銷售預測錯誤與盈餘預測錯誤之比例愈之影響較大，這顯示在台灣證券市場，分析師並未完全了解企業成本僵固性。而投資人對盈餘驚喜反應確實受分析師盈餘預測錯誤影響，然而在相同盈餘預測錯誤下，成本僵固性並不影響投資人對盈餘驚喜之反應。
This study examines whether Taiwanese companies’ cost stickiness affects analyst earnings forecast errors, analyst following, and analysts’ earnings forecast errors under favorable/unfavorable sales surprises. In addition, this paper also examines market response to earnings surprises for firm with different levels of cost stickiness.Empirical results show that cost stickiness has no significant impact on earnings forecast and the number of analyst following. However, taking sales forecast into consideration, the magnitude of earnings forecast errors under unfavorable sales is higher than the magnitude of earrings forecast under equivalent amounts of favorable sales surprises. This means that analysts do not fully recognize the effect of cost stickiness. In addition, investors’ reaction to earnings surprises are positively associated with by analysts’ forecast errors, but cost stickiness does not show incremental effect on this relationship